Step 1:

In bowl, whisk together flour, baking powder and soda, and salt. Grease two 9-inch/23 cm round cake pans. Line bottoms with parchment paper; flour sides.

Step 2:

In large bowl, beat butter until light and creamy. Beat in sugar, 1/3 cup (75 mL) at a time, on high speed until light and fluffy, about 3 minutes. Beat in eggs, 1 at a time; beat in rum and vanilla (mixture may look curdled but will come together). Gradually mix in flour mixture and buttermilk, making three additions of flour mixture and two of buttermilk.

Step 3:

Divide between cake pans, smoothing tops. Bake in centre of 350F/180C oven until tester inserted in centre comes out clean, 35 to 40 minutes.

Step 4:

Let cool on rack for 10 minutes. Slide knife around edges and remove from pans; peel off paper. Let cool on rack.

Step 5:

Molasses Buttercream: In heatproof bowl, whisk egg whites with sugar until frothy. Place over saucepan of boiling water; cook, whisking, until thermometer registers 110F/43C or finger can remain in mixture for no longer than 10 seconds, 1 to 2 minutes.

Step 6:

Beat with heavy-duty or stand mixer until cool, 7 to 10 minutes. Beat in butter, 1/4 cup (60 mL) at a time, until silky; beat in molasses and vanilla. Trim top of cake layers until level; spread with buttercream.

Step 1:Position rack in center of oven and preheat to 350°F. Butter three 8-inch-diameter nonstick cake pans with 1 1/2-inch-high sides. Place devil\’s food cake mix, 1 cup water, 1/3 cup vegetable oil, eggs, vanilla extract and 1/4 cup sour cream in large bowl. Using electric mixer, beat batter 2 minutes. Stir in 1 cup semisweet chocolate chips.

Step 2:Divide batter among prepared pans (about 1 3/4 cups batter for each). Bake until tester inserted into center of cake layers comes out clean, about 25 minutes. Cool cake layers in pans on racks 15 minutes. Run small sharp knife between pan sides and cake layers to loosen. Turn out onto racks; cool completely. Bring 1/2 cup raspberry jam and 3 tablespoons unsalted butter to simmer in heavy large saucepan over medium heat, stirring often. Remove from heat. Add remaining 3 cups semisweet chocolate chips and stir until melted. Add remaining 3/4 cup sour cream and 2 cups powdered sugar. Using electric mixer, beat frosting in pan until smooth and thick, about 2 minutes.

Step 3:Place 1 cake layer on platter. Spread 3/4 cup frosting over. Top with second cake layer. Spread 3/4 cup frosting over. Top with third cake layer. Chill cake until frosting sets slightly, about 15 minutes. Spread remaining frosting in swirls over top and sides of cake. (Can be prepared 1 day ahead. Cover with cake dome and let stand at room temperature.)