Make the browned butter

Cup of Yum
1. Melt the butter in a small skillet. Let it cook, stirring or swirling the pan often until the solids in the butter start to turn a nutty brown.
2. Watch carefully, this won't take very long, and the butter can burn easily. Remove the pan from the heat but keep warm.

Sweet potatoes

1. Peel and chop the sweet potatoes into even sized chunks.
2. Put the potatoes in a large pot and add cold water just to cover them. Add a teaspoon of salt and a few sage leaves (optional) to the pot. Bring to a gentle boil, then cook until the potatoes can be pierced easily with the tip of a sharp knife, about 10-15 minutes (or more, depending on the size of your potato pieces.) Drain well.
3. Add the hot potatoes to the bowl of a full sized food processor (mine is a 14 cup) and add the buttermilk and 3 tablespoons of the browned butter (reserve the rest for later.) Process until the potatoes have completely broken down. Then scrape down the sides of the bowl and process until the potatoes are completely silky. You can add more buttermilk if they seem very thick. Taste and add salt if necessary. This whole thing will only take a couple of minutes.
4. Spoon the potatoes into a serving bowl and swirl the top with the back of a large spoon. Top with a drizzle of the browned butter (reheated if necessary.) Garnish with fresh cracked black pepper and sage leaves if you like.