Special equipment: a 9-by-13-inch sheet cake pan
For the cake: Preheat the oven to 375 degrees F. Grease and flour a 9-by-13-inch sheet cake pan.
Melt the butter in a large saucepan, add 1 cup of water and bring the mixture to a boil. Remove from the heat and whisk in the flour and sugar until incorporated. Stir in the eggs, sour cream and almond extract. Pour the batter into the prepared pan and bake until golden on top, about 20 minutes. Cool the cake in the pan for 20 minutes.
For the ganache: Place the chocolate chips in a large heatproof bowl. In a medium saucepan, bring the cream and corn syrup to a boil, stirring to combine. Pour the cream mixture over the chocolate chips and whisk until smooth. Pour the ganache over the cake, using a spatula to cover the cake completely.