Preheat your oven to 350F, and line two 9” cake pans with parchment paper and butter.
In a big bowl, whisk together all the dry ingredients (except Ovaltine).
Mix the milk with Ovaltine in a cup.
Add eggs, oil, and Ovaltine milk to the dry mixture. Whisk until combined.
In another cup, mix boiling water with instant coffee, then whisk it into the cake batter.
Finally, fold in the sour cream—don't overmix.
Divide the batter into the pans and bake for 25-30 minutes (check with a toothpick).
Cool the cakes on a wire rack.