STEP 1: Preheat the oven to 350F (175C). Next, use a stainless steel bowl and grease it around the edges. The bowl should hold about 1.7 liters. Then, line the bottom of the bowl with a ring of greaseproof paper (3.5 inches in diameter).
STEP 2: Break the chocolate into a heatproof bowl. Add 25g/1oz of butter and place the bowl over a pan of gently simmering water until the chocolate melts (or melts in the microwave). Stir until the chocolate mixture is smooth.
STEP 3: In a separate bowl, combine the remaining butter with the sugar, eggs, flour, baking powder, and 85g/3oz of almonds. Whisk for 2-3 minutes until smooth and creamy. Scoop 350g/12oz of this mixture into another bowl and stir in the cocoa powder and milk. Stir the remaining almonds and vanilla extract into the remaining cake mixture. This step is crucial to the softness of your chocolate bomb cake.
STEP 4: Spoon a little of the vanilla mixture into the bottom of the bowl. Pour a spoonful of the cocoa mixture on top, then a little of the chocolate sauce, being careful not to let the chocolate sauce touch the edge of the bowl as it will burn while baking. Continue alternating the three mixtures in the bowl, adding large spoonfuls at random and spreading them out to mix the color. Smooth the surface, then swirl a skewer or the end of a teaspoon through the mixture, two or three times, to create ripples of color. Be careful not to overmix as the color will lose its clarity.
STEP 5: Bake for 30 to 45 minutes until the cake has risen and the top of the cake is firm to the touch. To test if the cake is done, insert a skewer into the cake lightly – the skewer should come out clean. Allow to cool in the bowl, then loosen the edges and invert the cake onto a flat plate.
STEP 6: Prepare the Chocolate Ganache First, heat the heavy cream in a small saucepan until it starts to simmer. Meanwhile, place the chocolate chips in a heatproof bowl and pour in the hot chocolate cream. Stir until smooth and glossy. Finally, let it sit for 2 to 3 minutes.
STEP 7: Chocolate Shell - the highlight of the chocolate bomb cake: Melt the semi-sweet chocolate chips in the microwave for 30 seconds. Stir until completely melted. Using a spoon or pastry brush, spread the melted chocolate into the inside of the silicone mold, making sure to spread a thin, even layer, enough to form a shell. Next, place the mold in the refrigerator for about 10 minutes, until the chocolate is completely set. Cover with a second layer of chocolate to ensure a firm shell, then chill again until set.
STEP 8: Assemble the Chocolate Bomb Cake: Place one layer of cake on a serving plate, and spread a thick layer of chocolate ganache on top. The second layer of cake will be placed on top of the ganache. Use the remaining ganache to cover the entire cake, creating a smooth surface. Carefully remove the chocolate shell from the mold. Place a hemisphere shell on top of the cake, then gently place the remaining hemisphere shell on top to form a complete dome over the cake.