For the crust
1/2 cup plus 2 tablespoons all-purpose flour
2 tablespoons unsweetened Dutch-process cocoa powder
1/4 teaspoon baking powder
1/4 teaspoon baking soda
1/8 teaspoon salt
2 ounces (4 tablespoons) unsalted butter
1/3 cup packed light-brown sugar
2 tablespoons plus 1 1/2 teaspoons granulated sugar
1 large egg yolk
1/2 teaspoon pure vanilla extract
For the filling
2 1/4 cups granulated sugar
1/4 cup plus 1 1/2 teaspoons all-purpose flour
1 tablespoon plus 1 1/2 teaspoonsunsweetened Dutch-process cocoa powder
2 pounds plus 10 ounces cream cheese, softened (from six 8-ounce blocks)
3/4 cup sour cream
3/4 teaspoon pure vanilla extract
3 large eggs plus 1 large yolk
6 ounces bittersweet chocolate (preferably 61 percent cacao), melted and cooled slightly
Boiling water, for pan
For the glaze
8 ounces bittersweet chocolate (preferably 61 percent cacao)
1 tablespoon corn syrup
1 1/4 cups heavy cream
For the decoration
Snake stencil 
Green and red* powdered food coloring
- Make the crust: Whisk together flour, cocoa powder, baking powder, baking soda, and salt in a large bowl. Beat butter and sugars with a mixer on medium speed until pale and fluffy, 2 to 3 minutes. Beat in yolk and vanilla. Reduce speed to low, and mix in flour mixture, scraping down sides of bowl as needed.
- Preheat oven to 350 degrees. Press dough evenly into bottom of a 10-inch springform pan** to form a 1/4-inch-thick crust. Let chill in freezer for 15 minutes. Bake until firm, about 15 minutes. Transfer pan to a wire rack, and let cool completely. Leave oven on.
- Make the filling: Whisk together granulated sugar, flour, and cocoa powder. Beat cream cheese with a mixer on medium speed until fluffy, scraping down sides as needed, about 3 minutes. Reduce speed to low. Gradually add the sugar mixture, and mix until smooth. Add sour cream and vanilla, and mix until smooth. Add eggs and yolk, 1 at a time, mixing just to combine after each addition. Add chocolate, and mix until combined.
- Wrap exterior of springform pan with a double layer of foil. Pour filling onto prepared crust, and set springform pan in a large roasting pan. Fill roasting pan with enough boiling water to reach halfway up the sides of springform pan. Bake cheesecake for 45 minutes.
- Reduce heat to 325 degrees. Bake until set but slightly wobbly in the center, about 30 minutes more. Turn oven off; leave cake in oven with door ajar for 1 hour.
- Transfer springform pan to a wire rack, remove foil, and let cake cool completely. Run an offset spatula or a knife around edge of cake, and carefully unmold. Set cake on wire rack set over a rimmed baking sheet.
- Make the glaze: Combine chocolate and corn syrup in a small bowl. Bring cream to a boil in a small saucepan over medium heat. Pour cream over chocolate. Let stand for 5 minutes. Whisk until smooth. (Do not whisk too much or bubbles will form). Let cool for 10 minutes.
- Decorate the cake: Pour glaze over cake in a circular motion, starting at the center and slowly moving outward toward the edge, to cover entire surface. Refrigerate, uncovered, until set, at least 4 hours (or overnight). Cake can be refrigerated for up to 2 days.
- Set snake stencil on cake: Print template. Place it under a sheet of calendar vinyl. Use a permanent marker to trace the outline and the snake design onto vinyl. Working on a cutting mat, use a craft knife to cut along the lines. Work slowly and carefully. The vinyl will dull the knife's blade; change the blade as necessary. Sift green powdered food coloring over snake, avoiding the tongue, Carefully sift red powdered food coloring over tongue.
*I used pink sugar instead of red, because that's what I had on hand.
**I made this in a 9-inch springform pan and had lots of leftover batter .
- Desserts, Cheesecake