*To brown your butter, place the unsalted butter over low heat and let it cook until small brown flakes form. You will want to stir or swirl the pan frequently to keep it from burning. The butter will foam and bubble up along the process, just keep stirring/swirling and move the foam aside from time to time to check the color. The butter will turn an amber/brown color and will smell nutty and toasted when it's ready. Pour melted butter and all the browned bits into a glass bowl to cool and solidify.Now is the time to make your salted caramel sauce - recipe below
Once browned butter has cooled at room temperature and is solid (about an hour), preheat your oven to 350°F. Prepare a 12 count muffin pan with liners. Set aside.
In a medium bowl, whisk together the all purpose flour, baking powder, baking soda and salt. Set aside.
In your stand mixer fitted with the paddle attachment or with a hand-held mixer, cream your solidified browned butter with the brown sugar and granulated sugar on medium for 2-3 minutes, until fluffy.
Add the eggs and vanilla and mix on medium for approximately one more minute.
With the mixer on low, add half the flour mixture and mix until mostly incorporated. Add the milk and sour cream and mix on low until mostly incorporated. Scrape up and down your mixer bowl and then add the final half of the flour mixture and mix on low until just combined.
Divide the batter between the 12 liners, filling them about ¾ full. You’ll get at least 12 cupcakes and potentially up to 14. Bake for 16-20 minutes or until a toothpick inserted in the center comes out mostly clean. Allow to cool completely before frosting.
To make the homemade salted caramel
Add one cup of granulated sugar to a medium saucepan and heat over medium, stirring constantly. Use a wooden spoon or a high heat resistant rubber spatula.
The sugar will start to melt. Then it will clump together before melting into a thick amber colored liquid.
When the sugar is fully melted, add the room temperature butter. The butter will cause the sugar to bubble rapidly, so use caution in this step.
Whisk the butter into the caramel until it is completely incorporated. I prefer using a whisk to keep the butter and sugar from separating, but your wooden spoon or spatula can work as well.
When your butter and sugar are fully incorporated, slowly add the heavy cream while continuing to whisk (or stir). Again, the mixture will bubble rapidly, so use caution.
Let the mixture boil for approximately one additional minute.
Remove from the heat and stir in ½ teaspoon of salt.
Carefully pour caramel into a heatproof container and allow to cool to room temperature before using. (you can always place it in the refrigerator for 15 minutes or so if needed, but you want it at room temperature before adding it to the frosting).
You will have left over caramel sauce, store covered in the refrigerator for up to two weeks.
To make the salted caramel frosting
In your stand mixer with the paddle attachment or with a hand-held mixer, cream butter and vanilla for approximately 2 minutes.
Scrape up and down the sides of your bowl and add the powdered sugar. Mix on low until incorporated, then increase the speed to medium high and beat until well combined, about 1 minute.
Add the cool and room temperature salted caramel and mix on medium high until light and fluffy, approximately 2 minutes. Add a pinch of salt if too sweet.