I got a pan on a medium heat and put a decent lump of butter in there and let it sit, spit and bubble until it had turned a deep hazelnut colour (I can not say enough about brown butter, it's delish great with pasta and the aroma is amazing). Then added a handful of sage leaves and 2 eggs and pureed it.I had about 600 grams of (floury) potatoes peeled and cubed and boiling until nice and soft.
Next time I'll have to remember the post from Ideas in Food and what they did to their potato skins, and the byproduct sounds like fun to play with.