Add the zest, orange juice, beer, sugar, cornstarch, salt, and yolks to a saucepan off the heat and whisk until well combined. Add the butter and place the pan over medium/low heat. Whisk until thickened, about 10 minutes. Allow to cool to room temperature. Add to a bowl, cover and refrigerate until chilled, at least 2 hours.
Preheat oven to 350°F (if you haven’t done so, set your butter out to come to room temp, and put your sweetened condensed milk in the fridge to prepare to make the frosting!).
Add the flour, sugar, baking powder, baking soda, and salt to a stand mixer fitted with a whisk attachment, whisk to combine.
Add the oil, beer, vanilla, and eggs. Stir on low speed until just combined, then drizzle in the melted white chocolate and melted butter (do not over mix).
Grease and flour 3 (9-inch) cake pans. Divide the cake equally between the pans.
Bake until the top springs back when lightly touched, 28-32 minutes. Allow to cool before removing from the pans.
Layer the cooled cake with the blood orange mixture spread between the layers. Cover loosely and refrigerate until chilled (cold cakes are much easier to work with), ideally overnight.
Add the room temperature butter and shortening to the bowl of a stand mixer, beat on high until the mixture is very white, light and fluffy. This will take about 5 full minutes, but it’s an important step in getting enough air into the frosting to make it light. Lower the mixer speed to medium, add the sweetened condensed milk and vanilla extract. Turn off the mixer, add the powdered sugar, then mix until well combined.
Spread with about 2/3 of the frosting mixture on the outside of the cake, refrigerate until chilled and the frosting is set.
Add the remaining frosting on to the outside of the cake in a smooth layer and as decoration.