Get out whichever heat-safe container you plan to transfer the brown butter to when it's done and set it next to the stove.
Cut the stick of butter into chunks so that it melts evenly.
Heat a skillet with stainless steel or light colored surface over medium heat. Don't wait for the skillet to get hot, add the chunks of butter immediately and stir them as they melt.
Continue stirring as the butter melts and the water content begins to boil away. The butter will boil vigorously and the entire surface will become covered in bubbles. Keep stirring!
Use the spatula to push the bubbles out of the way as you stir so you can see the butter particles dancing and swirling on the bottom of the skillet. When they start to brown it's up to you how dark you want the to get.
For light brown butter, pull the skillet off the heat as soon as you see the slightest hint of brown. For dark brown butter, keep the skillet on the heat, stirring constantly, as the milk far particles take on a darker color.
A few seconds before the butter reaches your desired level of darkness, pull the skillet off the heat and immediately transfer the butter into the heat-proof container you set aside in step 1.
Stir the brown butter a few times as it cools to evenly distribute the milk fat particles. To chill the butter to solid, place it in the fridge for at least an hour. Stir several times in the first 20-30 minutes.
Store like you would regular butter, in an airtight container in the fridge. Use in place of regular butter in any recipe.