1-Preheat and Prep Pans: Set oven to 350°F. Spray two 9-inch round pans with nonstick spray, line bottoms with parchment.

2-Bloom Chocolate: Mix 1 cup cocoa powder, 4 ounces chopped semisweet chocolate, and 1 rounded tablespoon espresso powder in a bowl. Pour 1 cup hot water over, stand 1 minute, whisk smooth. Stir in 3/4 cup buttermilk and 1 1/2 teaspoons vanilla. Set aside.

3-Mix Dry and Wet: Whisk 2 cups cake flour, 1 teaspoon baking powder, 1 teaspoon baking soda, 1 teaspoon kosher salt. In mixer with paddle, cream 1 cup room-temp butter and 2 cups sugar 3 to 5 minutes till light. Add 3 extra-large eggs one at a time, beating after each. Alternate dry ingredients in three additions with chocolate mix in two, starting/ending with dry. Divide batter, smooth tops.

4-Bake: 35 to 40 minutes till tester clean. Cool in pans 10 minutes, then racks fully.

5-Caramel Ganache: Chop 9 1/2 ounces semisweet chocolate, add 1 1/8 teaspoons kosher salt to bowl. Simmer 1 cup sugar + 1/4 cup water till dissolved, boil to deep amber (9 minutes, swirl no stir). Off heat, add 1 1/2 cups heavy cream (bubbles), stir to dissolve over medium. Pour over chocolate, add 1 teaspoon vanilla, stir smooth. Cool slightly.

6-First Layer Ganache: Place one cake in 9-inch springform or ring. Pour 1 cup ganache over, chill 30 to 45 minutes till set. Cover rest.

7-Stabilized Filling: Soften 1 package gelatin in 2 tablespoons cold water 10 minutes, warm to dissolve. Whip 1 1/2 cups chilled heavy cream, 1/2 cup confectioners’ sugar, vanilla bean seeds to soft peaks. Add gelatin, beat stiff.

8-Assemble Filling: Spread filling over set ganache, smooth, top with second cake. Cover, chill 6 hours or overnight.

9-Final Ganache Coat: Remove sides, trim leaks. On rack over sheet, warm remaining ganache pourable, pour/spread over top and sides. Chill 1 hour.

10-Serve: Room temp briefly, sprinkle flaky sea salt. Slice clean.