Step 1In a small pan, bring the cream to a simmer over high heat. Place the chocolate in a medium bowl and pour the hot cream over it. Let the mixture stand until the chocolate softens, about 5 minutes, then whisk until smooth.
Step 2Whisk in the chili powders. Let the mixture stand until completely cooled, about half an hour. With an electric mixer at medium speed, beat in the butter, one tablespoon at a time, until smooth. Do not overbeat. Cover with plastic wrap and keep at room temperature until ready to use.
Step 1Pour the whipping cream into a chilled medium mixing bowl. With an electric mixture on medium speed, slowly beat in the powdered sugar and vanilla. Turn the mixer to high and beat until stiff. Do not overbeat. Cover with plastic wrap and refrigerate until ready to use.
Step 1Heat the oven to 350 degrees. Butter two 9-inch round pans (2 inches deep). Line the pans with parchment and dust with flour. Tap out the excess.
Step 2Whisk the cocoa and boiling water in medium bowl until smooth. Whisk in the room-temperature water and let stand until the mixture cools.
Step 3Sift together the flour, baking soda, baking powder, salt and chili powder.
Step 4Beat the butter and sugar together with an electric mixture at high speed until the mixture is light in color and texture, about 2 minutes. Beat in the eggs one at a time, then the ground vanilla beans or extract.
Step 5On low speed, add the flour mixture in three additions, alternating with two additions of the cocoa mixture, scraping the bowl often until smooth.
Step 6Spread the batter evenly in the pans. Bake until a toothpick inserted in the center comes out clean, about 40 to 45 minutes. Cool on a wire rack for 5 minutes, then remove the cakes from the pans and cool completely.
Step 7Place one cake layer upside-down on a cake plate. Spread with all of the chocolate filling. Top with the other cake layer, right side up.
Step 8Spread a thin layer of the whipped cream frosting over the top and sides of the cake to affix any crumbs to the cake so they won't mar the white frosting. Then continue to frost the cake, trying not to disturb the first coat. Refrigerate (up to 8 hours ahead). If chilled, let stand 30 minutes before serving. Just before serving, decorate with flower petals.