Favorite White Cake

This white cake recipe is buttery and moist with the fluffiest crumb and creamiest vanilla buttercream. The tricks are to use cake flour egg whites and sour cream.
Ingredients
2 and 12 cups 295g cake flour spooned leveled
2 teaspoons baking powder
12 teaspoon baking soda
1 teaspoon salt
34 cup 12 Tbsp 170g unsalted butter softened to room temperature
1 and 34 cups 350g granulated sugar
5 large egg whites at room temperature
12 cup 120g sour cream at room temperature
1 Tablespoon pure vanilla extract yes Tbsp!
1 cup 240ml whole milk at room temperature
Vanilla Frosting
1 and 14 cups 282g unsalted butter softened to room temperature
5 cups 600g confectioners sugar
13 cup 80ml heavy cream
2 teaspoons pure vanilla extract or use clear imitation vanilla extract for stark white frosting
18 teaspoon salt
sprinkles for garnish
Instructions
Preheat the oven to 350F 177C. Grease two 9inch round cake pans line with parchment paper rounds then grease the parchment paper. Parchment paper helps the cakes seamlessly release from the pans. If its helpful see this parchment paper rounds for cakes video post.
Whisk the cake flour baking powder baking soda and salt together. Set aside.
Using a handheld or stand mixer fitted with a whisk attachment beat the butter on high speed until smooth and creamyabout 1 minute. Add the sugar and beat on high speed for 2 minutes until creamed together. Scrape down the sides and up the bottom of the bowl with a silicone spatula as needed. Add the egg whites. Beat on high speed until combined about 2 minutes. Then beat in the sour cream and vanilla extract. Scrape down the sides and up the bottom of the bowl as needed. With the mixer on low speed add the dry ingredients until just incorporated. With the mixer still running on low slowly pour in the milk until combined. Do not overmix. You may need to whisk it