Yes, you read that correctly. Bacon and chocolate -- everyone's favorite indulgences -- together at last. It's a perfectly decadent combination, and an ideal cake for a dad's birthday bash! The chopped bacon goes in the frosting, not the cake, so leave it out if you want a vegetarian-friendly dessert.
Preheat oven to 350 degrees F. Generously butter and flour two 8x2-inch round cake pans (if cake pans are 8x1-1/2-inch, make three layers or use two 9x1-1/2-inch layers); set aside. Place cocoa powder in a large bowl; gradually add boiling water, whisking until thoroughly combined. Set aside to cool. In a medium bowl sift together flour, baking soda, baking powder, and salt. Finely chop whole vanilla beans (or process in food processor until fine).
In a large mixing bowl beat butter, sugar, vanilla beans, and pure vanilla on medium-high until well combined. Beat in eggs, one by one, until light and fluffy, about 5 minutes, scraping down sides of bowl often. Add the sifted dry ingredients in fourths, alternating with cocoa liquid. Stir slowly to prevent splatter. Scrape sides of bowl. Beat on low about 3 minutes or just until combined. Pour batter into prepared baking pans, filling each about two-thirds full. Bake for 30 to 35 minutes or until the center is just barely set. Be careful not to over-bake; cake should slightly resist the pressure of your finger. Let cakes rest for 10 minutes, then remove from pans. Completely cool cakes on a wire racks.
Meanwhile, in a large skillet cook bacon until crisp. Reserve 1 tablespoon bacon drippings to use in Chocolate Frosting, if desired. Drain bacon on paper towels. Finely chop enough bacon to equal 1/3 cup. Set aside.
For the Chocolate Frosting, chop chocolate and place in a large bowl. In a small saucepan, bring 1-1/2 cups of the whipping cream just to boiling; pour over chocolate then add bacon drippings and liquid smoke. Whisk until smooth. Add remaining 1/2 cup cold cream; whisk to combine. Place in freezer for 30 minutes, whisking occasionally until spreadable. (Watch closely the last 10 minutes; frosting should remain glossy.) Stir the chopped cooked bacon into 1/2 cup of the frosting, if desired. Set aside.
Place one cake layer on a plate; spread with the 1/2 cup frosting with bacon. Layer with a second cake. Spread top and sides with remaining Chocolate Frosting. Cover and refrigerate. Before serving, let cake stand at room temperature for 30 minutes. Top with rose petals.