In a stainless steel skillet (or another light-bottomed pan) over medium-high heat, melt the butter, swirling the pan occasionally. The butter will begin to foam, which signals the water in the butter is boiling off. (Watch closely at this stage; browned butter and burnt butter are within seconds of each other.) Tiny brown specs of milk solids will begin to appear at the bottom of the pan; constantly stir and scrape these off using a spatula so they don't stick.

As soon as the butter turns chestnut brown and smells nutty, remove the pan from the heat. Pour the browned butter into a large, heat-safe bowl, making sure to get all the browned bits. Chill the brown butter in the refrigerator for 2-3 hours.

Once the brown butter has chilled completely, remove it from the refrigerator and let it rest at room temperature for 15-20 minutes before making the pound cake.

Preheat the oven to 350°F. Spray 3, 8×4-inch loaf pans with nonstick cooking spray, followed by lining each with parchment paper. Set aside.

In the bowl of a stand mixer with the paddle attachment, cream together the brown butter and sugar until light and fluffy, about 3-4 minutes.

Add eggs one at a time, making sure each one has been incorporated before adding the next one. Add vanilla and mix to combine, stopping to scrape the sides of the bowl as needed.

Alternating between the flour and milk, add each to the butter mixture, beginning and ending with the flour. Beat until just combined, making sure not to overmix.

Divide batter evenly into the prepared loaf pans (about 2 ½ cups of batter per pan). Bake for 65-70 minutes, or until a toothpick inserted into the center of each cake comes out mostly clean.

Remove from oven and allow to cool in pans for 10 minutes, then remove from the pans. Remove the parchment paper and let cool completely on wire racks.

Drizzle with extra brown butter for serving (optional).