To make the cake, preheat oven to 350 degrees F. Butter and flour 2 8-inch or 9-inch cake pans and line bottoms with parchment paper.

In a bowl, whisk together the coffee and cocoa powder until no lumps remain. Set aside. In another bowl, sift together the flour, salt, and baking soda.

In a large bowl, beat the sugar and eggs together until smooth and pale yellow in color. Stir in the sour cream, followed by the vegetable oil. Add the flour mixture all at once and stir until combined. Stir in the cocoa mixture and mix until smooth.

Divide the batter evenly between the prepared cake pans and bake until a toothpick inserted into the center comes out clean, about 25-35 minutes. Let cool in the pan for 10 minutes, then remove and place on a wire rack to cool completely. Can be made in advance: Cover cake layers in plastic wrap and store in fridge for up to 5 days or double-wrapped in the freezer for up to 2 months.

Whip heavy whipping cream to stiff peaks. Fold in sweetened condensed milk and vanilla. Divide into 5 bowls and color each red, yellow, green, blue and purple.

Line an 8 or 9-inch cake pan (whatever you used to bake your cake layers) with plastic wrap. Dollop alternating spoonfuls of the colored cream mixture into the pan, then take a knife and run it through the mixture a few times to swirl the colors together. Flatten the top with a spatula. Freeze for at least 4 hours.

Whip heavy whipping cream, sugar, and vanilla to stiff peaks.

Place one cake layer on a plate or cake stand. Remove ice cream layer from pan and plastic wrap and place on top of cake layer. Top with remaining cake layer.

Cover with whipped cream and decorate with rainbow chips/sprinkles as desired. Freeze for at least 1 hour before serving. Let sit at room temperature a few minutes before slicing with a sharp knife. Store leftovers in the freezer.