• Preheat your oven to 350°F (or 177°C) and spread light, nonstick cooking spray over a 5 x 9 loaf pan.

Cake Batter

• Grab a big bowl and whisk your cake flour, baking soda, baking powder, and salt. Then, in another bowl, mix your melted butter, egg, milk, sour cream, granulated sugar, and vanilla until it's all nicely smooth.
• Combine wet and dry ingredients into one bowl and gently whisk everything. Don't go overboard. Toss in the colorful sprinkles.
• Spread that batter into your loaf pan. Bake for 45 minutes to 1 hour (give or take). After the first 25 minutes, cover it loosely with aluminum foil to keep the top surface from getting too dark.
• Test the cake with a toothpick (if the toothpick is mostly clean when you pull it out, your cake is ready). Put the pan on a wire rack to let the cake chill entirely.
• Carefully lift your cooled cake off the pan and lay it on your cutting board. Slowly and horizontally slice it into three even layers.

Ice Cream Layers

• Bring out the frozen ice cream. Let it sit at room temperature for about 15 minutes to soften (or zap it in the microwave for 25 seconds if you're in a hurry).
• Line your prepared cake pan with outer plastic wrap or parchment paper, leaving enough hanging over the sides.
• Drop your bottom cake layer onto the pan, then carefully spread one pint of the now-soft ice cream on top. Pop on the center cake layer, then smooth out another pint of soft ice cream on top of it. Finish it off with the last cake layer, giving it a gentle press.
• Cover it all with outer plastic wrap or foil and freeze it for 8 hours to 3 days. If you're freezing it for more than a day, let it rest at room temp for about 10 minutes before pouring on the ganache in the next step.

Ganache

• 15 to 17 minutes before you take the cake out of the freezer: Chuck your chopped chocolate into a heat-safe bowl. Heat heavy whipping cream (or heavy cream) over medium heat in a saucepan until it starts to simmer gently.
• Pour that hot cream over the chocolate and let it rest for a few minutes. Then, slowly stir till the chocolate is melted and smooth.
• Now, set it aside for about 10 mins to thicken up.

Assembly

• Release the cake from your freezer! Hold the parchment paper hanging over the sides of the pan and carefully lift the whole thing out. Plop it onto a medium cutting board.
• Spread the ganache all over the top of the cake. Optional: Toss on some sprinkles.
• Give the cake 5 minutes to soften before slicing. Enjoy your homemade cake!