Heidi from 101 Cookbooks also does a version with peas, which she says is good with the cumin butter. In fact, she says it's nice to have the cumin brown butter on hand, so if you think it sounds like something you might like make a double or triple batch of it. 1 tsp. cumin seeds 1/4 cup unsalted butter fine grain sea salt __ 3 Tbsp. unsalted butter 2 med. yellow onions (or equivalent fresh onions), chopped 2 med. garlic cloves 1 lb. potatoes, cut into 1/4" cubes 2+1/2 lbs. yellow summer squash, cut into 1/2" slices 4 c. vegetable stock 1 c. buttermilk 1 bunch of chives, chopped
In a skillet, over medium heat, toast the cumin seeds until they are fragrant. Just a minute or two. Use a mortar and pestle to pound the seeds into a fine powder. Alternately, you can use an electric spice grinder. Set aside. In the same skillet, melt the butter and cook until it's brown and gives off a deliciously nutty aroma. Remove from heat, stir the cumin into the butter along with a generous couple pinches of salt, then set aside in a warm place. You want the butter to stay liquid until you're ready to use it.
To make the soup, heat the butter in your largest pot or stockpot over medium-high heat. Add the onions, garlic, and a bit of salt. Saute for a few minutes, or until the onions start to get translucent. Stir in the potatoes and squash and cook for another 7-10 minutes, or until the squash starts to soften up. Stir in 3 1/2 cups of the stock (most of it) - the stock should just barely cover the vegetables. Bring to a boil. Reduce heat to a simmer and cook until the potatoes are tender, roughly another 25 minutes. Remove the soup from heat, puree completely with a hand blender, then stir in the buttermilk. If you need to thin the soup out with a bit more stock, you can do so. Taste and add more salt if needed. Serve each bowl topped with plenty of the cumin butter, and a sprinkling of chives.
(slightly) adapted from 101 Cookbooks http://www.101cookbooks.com/