Preheat oven to 325°F (170°C). Spray 2 (8-inch) round cake pans with baking spray with flour.

In a medium saucepan, melt butter over medium heat. Whisk in cocoa; cook until fragrant, about 1 minute. Remove from heat; whisk in brown sugar, hot coffee, and buttermilk until sugar dissolves. Whisk in eggs and vanilla.

In a medium bowl, whisk together flour, baking powder, baking soda, and salt. Gradually add flour mixture to cocoa mixture, whisking just until combined. Divide batter between prepared pans (about 3 cups or 685 grams each).

Bake until a wooden pick inserted in center comes out with a few moist crumbs, 40 to 45 minutes. Let cool in pans for 10 minutes. Invert cake layers onto a wire rack, and let cool completely.

Place 1 cooled cake layer on desired serving platter.

Unwrap cold Pistachio Kataifi Filling, and place on cake layer. Top with remaining cake layer. Spread Chocolate Buttercream on top and sides of cake. Pour Chocolate Ganache onto cake, using an offset spatula to push over edges. Garnish with reserved praline, if desired. Cover and refrigerate for up to 3 days.

In a large heavy-bottomed saucepan, melt butter over medium-low heat. Add kataifi; cook, stirring constantly, until golden brown, 12 to 15 minutes. Transfer to a large bowl; let cool completely.

Line a rimmed baking sheet with heavy-duty foil; lightly spray with cooking spray.

In a medium saucepan, stir together granulated sugar, ¼ cup (60 grams) water, and corn syrup. (Mixture should resemble wet sand.) Bring to a boil over medium heat, stirring just until sugar dissolves. (Do not stir once mixture starts to boil.) Cook, brushing sides of pan with a pastry brush dipped in water, until mixture is a light amber color and a candy thermometer registers 300°F (149°C) to 310°F (154°C), 8 to 10 minutes. Remove from heat, and quickly stir in pistachios, sesame seeds, baking soda, and salt. Pour onto prepared pan. Using a heatproof spatula, carefully spread mixture into a single layer. Let cool completely.

Roughly chop or break candied pistachio brittle into small pieces; reserve 2 to 3 tablespoons (about 20 to 30 grams) for cake garnish, if desired.

In the work bowl of a food processor, process remaining pistachio brittle until a thick, dough-like paste forms, 4 to 6 minutes. Add cream, confectioners’ sugar, melted butter, and food coloring (if using), and process until mixture is smooth, 2 to 4 minutes, stopping to scrape sides of bowl. Stir pistachio mixture into toasted kataifi until well combined.

Line an 8-inch round cake pan with plastic wrap, letting excess extend over sides of pan. Spread pistachio mixture into an even layer in prepared pan. Cover with excess plastic wrap, and refrigerate for at least 1 hour before using.

In the bowl of a stand mixer fitted with the paddle attachment, beat butter and salt at low speed until smooth.

In a large bowl, sift together confectioners’ sugar and cocoa. With mixer on low speed, add sugar mixture, about 1 cup at a time, to butter mixture alternately with cream, about 1 tablespoon (15 grams) at a time, beginning and ending with sugar mixture, beating until smooth after each addition and stopping to scrape paddle and bottom and sides of bowl. Beat in vanilla. Increase mixer speed to medium, and beat until fluffy, 2 to 3 minutes. Use immediately.

In a small saucepan, heat cream over low heat until steaming. (Do not boil.)

In a medium heatproof bowl, combine hot cream and chocolate; let stand for 3 minutes. Whisk until chocolate is melted and mixture is smooth. Let cool slightly before using.