Adapted from the recipe described in the Noma Guide to Fermentation. The garum evaporates, leaving a crust of umami salt. You could also make these with mushroom catsup. Peanuts or hazelnuts would work too.
Preheat an oven to 325. Put the nuts in a 10 inch saute pan, preferably a cast iron skillet or a non-stick pan with concave sides for easy tossing. Being able to toss and coat the nuts quickly is essential to completely covering them with the coating. Toast the nuts for 15 minutes, or until nicely browned. Turn the oven off.
Then, working quickly, and having the meat garum at the ready, put the pan with the nuts on a burner on high heat. Add the garum, it should sizzle and sputter.
Cook the nuts for a few seconds to quickly evaporate the liquid, tossing the nuts to coat them. When the liquid is evaporated, turn the heat off, transfer the nuts to a small plate or baking dish and allow them to dry in the oven ajar, with the heat turned off.
When the nuts are cool, they'll be coated in a crisp, salty covering. They were so good I ate all of them in a sitting. Mushroom ketchup would be an excellent substitute here for the meat garum, too.