Prepare and bake both the yellow cake and devil's food cake mixes according to the package directions in separate 9x13 inch baking dishes.

Let them cool completely.

In a medium saucepan over medium heat, melt the sugar, stirring constantly, until it turns a deep amber caramel.

Carefully stir in the butter until melted and smooth.

Slowly pour in the heavy cream, stirring constantly. The mixture may bubble vigorously.

Cook, stirring, until the caramel is smooth.

Stir in the toasted sliced almonds and almond extract (if using).

Remove from heat and let it cool slightly.

In a medium saucepan, whisk together the sugar, cornstarch, and salt.

Gradually whisk in the heavy cream until smooth.

Cook over medium heat, stirring constantly, until the mixture thickens and comes to a boil.

Reduce heat and simmer for 1 minute, stirring constantly.

Remove from heat and stir in the vanilla extract.

Cover the surface of the pastry cream with plastic wrap to prevent a skin from forming. Let it cool completely.

Place the chopped chocolate in a heat-proof bowl.

In a small saucepan, heat the heavy cream until just simmering.

Pour the hot cream over the chocolate and let it sit for 1 minute.

Stir until the chocolate is completely melted and smooth.

If the cakes have domed, level them with a serrated knife.

Place the devil's food cake layer into the bottom of the 9x13 baking dish.

Place the yellow cake layer over the almond caramel layer.

Pour the chocolate ganache over the top, spreading it evenly to cover the entire surface.

Chill the cake in the refrigerator for at least 2-3 hours, or until the pastry cream is set and the ganache is firm.

Slice and serve chilled directly from the 9x13 inch dish.