Preheat oven to 325°F (163°C). Grease a 9 x 5-inch loaf pan and line with parchment paper.
Cream butter and sugar in a stand mixer on medium-high speed for 4-5 minutes until light and fluffy.
Add eggs, one at a time, followed by the egg yolks, and mix until smooth.
Stir in vanilla extract until fully combined.
Combine the flours, baking powder, and salt in a separate bowl. Gradually add to the wet mixture, alternating with milk, until just combined.
Pour batter into the prepared pan, smooth the top, and bake for 60-65 minutes. Check for doneness by inserting a toothpick — it should come out clean or with a few crumbs.
Cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.
