Place 4 tablespoons of vegan butter in a small heavy saucepan and turn to medium heat. (A light-colored pan makes it easier to see when it has browned.)
Allow the butter to melt and begin to slowly simmer and get foamy. Once the butter has melted turn the heat to medium-low. Pick up the pot and swirl it around about once every minute to avoid scorching. (Or simply stir the butter with a whisk every minute or so.)
After the butter has slowly simmered for about 10 minutes, the foaming will start to reduce, it will start to smell nutty, and you will see small brown flecks at the bottom. At this time, remove it from the burner.
To make brown butter sage sauce
After the butter has browned, immediately add 3 cloves of fresh minced garlic and 5 sage leaves and let them sit and infuse into the butter for about 5 more minutes before using.
Notes
Be sure to use high-quality vegan butter. You will not get good results from inexpensive vegan margarine with a lot of water content.
Cook your brown butter over low heat. Take your time and be patient, you don't want to burn your butter.
You want the butter to have little brown specks in it and have a nutty aroma. If your butter has black specks and smells burnt, throw it out and start again.
If you are used to making brown butter from dairy butter, this non-dairy version will not have as many brown specks in it.