For the Cake:
1 ¾ cup AP flour
1 tsp. baking powder
¼ tsp. fine sea salt
10 tbsp. unsalted butter
1 ¼ cup granulated sugar
5 large eggs
1 tsp. pure vanilla extract
Boozy Coffee Soak (Makes about 3 1/3 cups)
½ cup whole milk
1 (14 oz) can sweetened condensed milk
1 (12 oz) evaporated milk
½ cup strong brew coffee
1 tbsp. instant espresso
3 tbsp. Frangelico (optional)
Whipped Cream Frosting (Makes about 4 ½ cups)
1 pint heavy cream
3 tablespoons granulated sugar
Rainbow sprinkles for garnish
Preheat oven to 350 degrees. Butter a 9x13 cake pan and line with parchment paper.
Whisk together the three milks with the coffee, espresso and Frangelico if using; set aside.
In the bowl of a stand mixer fitted with paddle attachment, beat the butter until smooth and creamy, about 3 minutes. Add in the sugar and beat until light and fluffy, another 3-5 minutes. Add in the vanilla and then the eggs one at a time and continue mixing until fluffy. With the motor on low, gradually add the flour about ¼ cup at a time. Beat until just mixed.
Pour batter into prepared pan and bake for 20-25 minutes, or until a toothpick inserted in the center comes out clean.
Transfer the cake pan to a cooling rack and allow it to cool for about an hour. Once cool, use a fork or toothpick to poke holes all over the cake. Pour the coffee-milk mixture evenly over the entire cake, cover with plastic wrap and refrigerate for at least 2 hours and up to overnight.
When ready to serve, frost the entire cake with whipped cream frosting and garnish with rainbow sprinkles.