INGREDIENTS
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1 box white cake mix, 15.25 oz
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1 cup sugar
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1 cup all purpose flour
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3/4 tsp salt
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4 egg whites
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1 cup milk
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1/2 cup buttermilk
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1 cup sour cream
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2 sticks butter, room temperature
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1/2 cup vegetable shortening (can be replaced with butter)
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1 tsp vanilla extract
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3-4 cups powdered sugar