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1
Preheat the oven to 350F.
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2
Grease and flour two round 9 x 2-inch cake pans.
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3
Pour about a tablespoon of flour into each of the pans and roll it around, tapping as you go, until the sides and bottom are covered completely with a thin layer of flour.
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4
Tip the pans and tap out excess flour.
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5
In a large mixing bowl, mix thoroughly with a whisk the flour, baking powder, salt, and baking soda.
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6
In a separate large bowl, beat the butter with an electric mixer until creamy, about 30 seconds.
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7
Add the sugar in 1/2-cup measures, beating about 15 seconds after each addition and scraping down the sides of the bowl if necessary, until the mixture has lightened in color and become fluffy, about 2 minutes.
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8
Add the eggs and egg yolks, one at a time, and the vanilla, beating for 15 seconds after each addition.
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9
Add the flour mixture to the butter mixture in thirds, alternating with additions of the milk.
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10
To avoid overmixing the batter, mix gently with a wooden spoon or rubber spatula after each addition, until the ingredient is just incorporated.
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11
Beat until all the ingredients have been incorporated, and then just a few strokes beyond.
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12
Divide the batter between the cake pans and spread the tops evenly.
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13
Bake until a cake tester or toothpick emerges clean, about 30 minutes.
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14
Remove from the oven and let the cakes cool in their pans on a rack for 10 minutes, then slide a thin paring knife around the edge of the pans and invert the cakes.
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15
Turn each cake again so its rounded top is facing up and cool the cakes completely on the rack.
