Brown Butter Icing is made with nutty, caramel-like, fragrant, toasty, rich brown butter. This Brown Butter Icing is practically a perfect substance. Smooth, rich, sweet, and beaming with all the flavor and benefits of brown butter. And it goes with everything!
Place the powdered sugar in a medium bowl, and set aside.
Melt butter in a small saucepan over low-medium heat, stirring frequently, until it foams, the foam dissipates, it turns a deep golden brown, and develops brown flecks and a nutty fragrance, about 10 minutes or so. Toward the later stages, around the time it begins to foam, watch the brown butter very closely. It can go from 'brown' to 'burned' very quickly.
Remove from heat, cool 2-3 minutes, and *carefully* pour over powdered sugar.
Add milk and vanilla, and vigorously whisk the mixture until smooth. If the icing seems to seize or separate, you just need to reeeeeeally mix it to emulsify it. You can use an electric mixer if preferred. But don't give up thinking it's ruined, it just needs to be emulsified, so give it a serious mixing! Icing should be thin enough to spread, but not runny or drippy. Add additional milk or powdered sugar, as needed, to achieve desired consistency.
Frost cakes, cookies, breads. It is an icing that sets. However, if you plan to use this frosting at a later time, it will freeze beautifully. Seal it in an airtight container and freeze. When ready to use, thaw to room temperature, and then microwave for 20-30 seconds -- that's it -- to thin it out.
I love the warmth that cinnamon and/or pumpkin pie spice add to Brown Butter Icing. I think spice takes this to another level! If you'd like, as I have in the photos, you can whisk in 1/2 tsp. of either or each!