Pi Day: Serve up a slice of rich chocolate cream pie

Pi Day on March 14 is celebrated in all kinds of binary ways, but the sweetest approach is to measure that diameter across your favorite pie filling.

If you are celebrating Pi Day on Friday, March 14 (3.14), you will be in brilliant company, literally. For math lovers, it is a profound day to ponder the near-sacred number and its ubiquitous meaning and infinite form, which has intrigued mathematicians since Archimedes.

And it is, indeed, truly special – even a brief glance through the Pi Day official website leads me to question how I could have missed out on the great, collective love for pi. There are pi-stories, pi-poems, even pi-digit memorization contests, albeit for the truly pious. MIT is said to organize its application decision letters on this date, and perhaps most extraordinary of all, it is the date of Albert Einstein’s birthday.

For others, Pi Day is a perfect pastry homophone, as naturally “pi” can be easily construed as “pie,” so why not celebrate both? It is like a numerical baker’s fate – two vastly different concepts – yet the “ratio of the circumference of a circle to its diameter” can hold many meanings, and math, on this day, your favorite sweet filling. Flour Bakery in Cambridge, Mass., shared its recipe for Rich Chocolate Cream Pie to commemorate the greatness of all things π.

I must concede this is my favorite pie at Flour Bakery – it is a rich equation of airy whipped cream that sit atop like perfectly formed clouds, a decadent, soft chocolate custard filling, and confectionery pie crust that beholds a perfectly blissful note of sweet and crunchy. While I cannot explain my love for this pie in mathematical terms – I truly wish I could – I do know it is as infinite and inexplicably adored as pi itself.

Rich Chocolate Cream Pie

Recipe courtesy of Flour Bakery in Cambridge, Mass., as adapted from the cookbook “Flour” by Joanne Chang. Published by Chronicle Books, 2010.

Makes one 9-inch pie

Serves 8

1 Pâte sucrée 9-inch pie shell [or use a ready made pie shell to save time] 

6 ounces (168 grams) bittersweet chocolate (62 to 70 percent cacao), chopped

3/4 cup (180 grams) half-and-half

2-1/2 cups (600 grams) heavy cream

4 egg yolks

1/3 cup (70 grams) granulated sugar

1/4 teaspoon vanilla extract

1/4 teaspoon kosher salt

3 tablespoons confectioners’ sugar

1 tablespoon cornstarch

3- to 4-inch slab milk chocolate, at warm room temperature, for decorating

1. Bake the pie shell. Remove from oven, sprinkle with 1 ounce (25 grams) of the bittersweet chocolate, and return to the oven for about 30 seconds. Remove from the oven and using a pastry brush, paint the bottom and sides of the shells with melted chocolate. This will protect the shells from becoming soggy when pouring in the chocolate filling. Set pie shell aside.

2. In a medium sauce pan combine the half-and-half and 1 cup (240 grams) of the cream and scald over medium-high heat (bubbles will begin to form around the edge of the pan, but the liquid is not boiling). Meanwhile, place the remaining 5 ounces (140 grams) of the bittersweet chocolate in a medium heatproof bowl. Place over (not touching) barely simmering water in a saucepan and heat, stirring occasionally, until completely melted and smooth. Remove from the heat. Pour the hot cream mixture over the melted chocolate and whisk until thoroughly combined.

3. Place the egg yolks in a medium bowl, and slowly whisk in the granulated sugar. Slowly pour the hot cream-chocolate mixture, a little at a time, whisking constantly. When all of the cream-chocolate mixture has been incorporated, return the contents of the bowl to the saucepan, and return the saucepan to medium-low heat. Cook, stirring continuously with a wooden spoon and making sure to scrape the bottom of the pan often to prevent scorching, for 6 to 7 minutes, or until the mixture thickens and coats the spoon thickly. To test, draw your finger along the back of the spoon; the custard should hold the trail for a couple of seconds before it fills. (First, the mixture will be liquid and loose, and then it will start to get a little thicker at the bottom of the pan. As it continues to thicken, it will start to let off a little steam. When you see wisps of steam steadily rising from the pan, you know the filling is almost done.)

4. When the custard is ready, immediately strain it through a fine-mesh sieve into a heatproof pitcher or bowl, and stir in the vanilla and salt. Pour the filling into each chocolate-lined pie shell and refrigerate, uncovered, for about 8 hours, or until set, or up to overnight.

5. Fit the stand mixer with the whip attachment (or use a handheld mixer) and whip together the remaining 1 and 1/2 cups (360 grams) cream, the confectioners’ sugar, and cornstarch until stiff peaks form.

6. Pile the whipped cream on top of the chocolate filling, spreading it to the edges of each pie. Using the back of a small knife or a vegetable peeler, shave curls from the milk chocolate slab. (Make sure the chocolate is slightly warm, or splinters will form instead of curls.) Decorate the pies with the curls.

7. The pie can be stored in an airtight container in the refrigerator for up to 2 days.