Instructions

1. The first step is to make a batch of Brown Butter.  Place 1/2 cup of butter in a skillet on medium heat. Melt the butter and then allow it to continue to simmer on medium heat. The melted butter will start to bubble and foam will appear and then brown crystals will begin to form.  This is the good stuff.  
2. Stir every 30 seconds for about 6-7 minutes.  This is what it should look like when it has reached the "brown butter" stage.  It will be golden brown, with yummy bits of brown butter goodness floating in the melted butter. When you reach this stage take the brown butter off the heat and pour it into a glass bowl or measuring cup to cool on the counter, not the refrigerator.  It should be ready in about an hour.
3. Add the butter and the brown butter to a mixing bowl.  Use a spatula and make sure you get every bit of the yummy brown butter solids into the mixing bowl.  That's the stuff that makes this frosting taste sooooo good.  The regular butter should be "slightly softened" which is somewhere between just out of the refrigerator and room temperature.
4. Mix the butter and the brown butter together on medium speed until thoroughly combined (about 2 minutes.)  You really want the brown butter to meld with the butter to enhance the flavor of the frosting. Use a spatula to scrape the butter mixture down from the sides of the bowl.  
5. We use a food scale to measure 1 Pound of Powdered Sugar.  If you don’t have a food scale, measure 4 cups instead. We normally do not sift the powdered sugar and instead rely on the mixer to do that work for us.
6. Add the powdered sugar to the brown butter mixture in the mixing bowl.
7. Here is a Two Sisters Tip – cover the mixer with a towel during this part of the mixing process to keep the powdered sugar from flying out of the mixer.
8. Start your mixer (or electric beater) on the lowest setting and keep it on low until the butter and sugar are incorporated (about 30 seconds). Stop the mixer and scrape down the sides of the bowl and then increase the speed to medium-high and mix for another 30-45 seconds so the frosting gets light and fluffy. If necessary, add 1 tablespoon of milk and mix until it is the frosting right consistency.  Continue to add milk a teaspoon at a time until it is the right consistency.   
9. Taste your frosting.   You are trying to determine if the consistency is wrong and if it needs more milk.