Pi Day: Rosewater πstachio Reuleaux Triangle Hamantaschen

Pi Day: Rosewater πstachio Reuleaux Triangle Hamantaschen

I think sometimes, as people who live in privilege, we forget we are standing on the shoulders of our neighbors around the world. Case in point, the GOP’s intervention in our negotiations in Iran, written in a tone that implies the people of Iran are incapable of understanding the intricacies of government, much less the complexities of nuclear physics.

As the GOP attempts to “educate” Iran, they might think about brushing up a bit on basic math. People who probably joke about “weapons of math destruction” don’t realize that the word algebra, in fact, comes from the title of Persian book written somewhere around 780 AD: ilm al-jabr wa’l-muḳābala ‘The Science of Restoring What Is Missing and Equating Like With Like.’ (isn’t that a poetic description of algebra?) The author of the book, Abū ‘Abdallāh Muḥammad ibn Mūsā al-Khwārizmī, is considered to be the father of Algebra.

Yes – Algebra, the root of most of our technology, including nuclear physics, was born in Iran – once known as Persia. al-Ḵwārizmī, an orthodox Muslim, had such an enormous effect on our mathematical thinking that we invoke his name every time we use the word algorithm. NASA scientists named a lunar crater for him in honor of his contributions to science. Not only did al-Ḵwārizmī develop algebra and quadratics (a subject Sparky currently wrestles at school) but he also popularized the decimal system.  (A bit of trivia: al-Ḵwārizmī’s numbering system was the subject of the first “new math” panic: it was outlawed in Italy until Fibonacci interceded in 1299)

Another famous Persian you may be more familiar with, Omar Khayyam, was much more than “people lying out in the woods eating sandwiches, and drinking directly out of jugs with innocent young girls” While we know him best as the poet author of Marian Paroo’s beloved Rubaiyat, in his time he was revered as a mathematician and philosopher. He is known for using geometry to solve third-degree equations by graphing the intersection of a parabola and a circle. (He also has a lunar crater!)

So, how do we bring this around to Pi Day? Well, among other things, al-Ḵwārizmī used his decimal place system instead of the previously used clunky fractions to calculate Pi as 3.1416 (remember that the last digit would be rounded up, right?) (the prior advance almost 300 years before was by Japanese mathematician Tsu Chung Chi: 355/113) So, this year, we use the “ultmate Pi Day” to honor the Persian contributions to math, and created a pie with tradiational Persian flavors: pistachio, rosewater and cardamom.

Since an angle is really nothing more than a section of a circle, Pi has just as much to do with corners as it has curves. Reuleaux triangles are a deceptively simple shape: a triangle whose sides have been rounded off with curves…but using three circles to create a rounded triangle produces a nearly magical triangle of constant width. You can do all kinds of cool things with a Reuleaux triangle: make non-circular wheels, manhole covers that won’t fall in the hole when turned, coins that will work in vending machines, engines, and even drill a square hole. The area of a Reuleaux triangle is calculated as ½(π – √3)s2 and although it is not the only shape of constant width, it is the smallest in area. The area of each curved portion of the Reuleaux triangle is a circular segment with opening angle 0=π/3. Thus, π figures prominently in our pie.

Since we settled on a triangle, we have to discuss our favorite triangle-shaped pastry, the Hamantaschen. A pastry of Yiddish origin, it is named for the biblical character Haman…who is, interestingly enough, Persian. The pastry is supposed to be triangle-shaped like Haman’s hat, and is eaten during the Jewish holiday of Purim. As the story goes, the beautiful Queen Esther successfully prevents the royal vizier, Haman, from murdering all Jews in Persia by revealing to her husband, the King of Persia, that she is a Jew. (While this bible story leans more towards lore and less towards historical fact, the Persian emperor Cyrus the Great did indeed liberate the Jews from Babylon and allow them to return to Israel to practice their religion freely, as described in the book of Ezra.) A Persian Jewish population still exists in Iran – who, apparently, make pistachio rosewater cookies for Purim.

So, we are able to tie up our math, geometry, politics and history in a neat bow with this delicious pastry that I hope you will enjoy.

Dough Ingredients

  • 2 cups all-purpose flour
  • 1/4 cup sugar
  • 1/8 teaspoon salt
  • 1 stick (1/2 cup) butter
  • 4 ounces (1/2 cup) cream cheese (we used neufchatel)
  • 1/8 – 1/4 tsp rosewater
  • 1 egg yolk (use a large egg)

Filling ingredients

  • 1 1/4 cup ground pistachios (reserve a pinch for decoration)
  • 3/4 cup granulated sugar
  • 2 eggs
  • 6 tablespoons butter
  • 1/2 teaspoon vanilla extract
  • 2 tablespoons flour
  • 1 cardamom pod

Both the dough and the filling will need time to chill in the refrigerator, so plan accordingly.

Make the dough:

IMG_2802Using a food processor, chop the butter, cream cheese, and sugar for a few pulses. Add the rosewater and flour and process until the butter is the size of peas, then add the egg yolk and process until lightly blended (the dough will be shaggy.) Turn the dough out onto a clean surface and push it together until loose dry ingredients are incorporated – then refrigerate in a ziploc bag or covered container for at least an hour.

IMG_2823Make the filling: if whole, shell and then grind your pistachios with the cardamom into meal using a food processor or blender (we used the same food processor as the dough, it’s not necessary to clean out the dough scraps.) Add all the filling ingredients to your blender and blend to a smooth paste. Pour the filling into a bowl, cover it, and refrigerate for an hour or more.


IMG_2826Shape your Reuleaux triangle: we used our largest 10″ springform pan ring to guide our arc. (we made tart-size Hamantaschen, but you can make them the traditional cookie size if you prefer.) Starting with an equilateral triangle scribed on aluminum foil, Sparky used the tightest arc* of the pan to round off the edges.









Preheat your oven to 350 and set out a cookie sheet. Roll out your chilled dough to 1/8 thickness and cut it into a circle at least an inch larger than your triangle. Using the scribed aluminum foil and your springform pan as a guide for the first curved side of your triangle, fold the crust up against the side of the pan.

Spread filling from the center towards the edge supported by the pan, and then fold the crust over the filling. Repeat with the other two sides, folding the dough lightly to help it fit the curve and pinching it together firmly at each apex.

Sprinkle the top with ground pistachios, slide the tart, aluminum foil and all, onto your cookie sheet. Bake at 350 for about 20 minutes, or until the filling puffs up and both crust and filling brown lightly.

Dust with powdered sugar, serve and enjoy!


* The easiest way to figure out the length of the sides in relationship to your circle is to use a compass set to the length of the radius of your pan, draw an arc, then move the leg of your compass to that arc and draw another arc that intersects the first. Move the leg of your compass to the intersection point and draw a third arc that intersects the other two: you have your Reuleaux triangle.

And now, my friends, on this Pi Day of Pi Days, I realize that the time has come for me to step aside and allow Sparky to write his own story. I have been keeping this chronicle of our cooking adventures for over half his life and one day I suddenly looked up and found him to be a fine, independent young man ready to veture out on his own path.

With this post, I bid a fond adieu to Sundays with Sparky and look forward with much anticipation to the chapters he will create for himself. Thank you for coming along with us!

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