Preheat the oven to 325°F. Line an 8 x 8-inch baking pan with parchment paper and set aside.

In a large mixing bowl, add the egg yolks, flour, sugar, and ½ cup of the milk. Beat on high speed until the mixture is completely smooth with no lumps.

Once smooth, slowly add the remaining 1 1⁄2 cups milk, reduce mixer speed, and mix until just combined. The batter will be thin.

In a separate, completely clean bowl, beat the egg whites on high speed until stiff peaks form. Be sure the bowl and beaters are free of grease or residue.

Gently fold ⅓ of the whipped egg whites into the batter using a spatula, folding from the bottom to fully incorporate.

Fold in the final third gently, leaving a few small streaks or lumps of egg white. The batter should look light and airy.

Pour the batter into the prepared pan and bake for 40–50 minutes, or until the top is evenly browned and a toothpick inserted into the center comes out clean. If unsure, bake for an additional 5 minutes.

Let the cake cool completely before removing from the pan and slicing. The cake will naturally deflate slightly around the edges as it cools.