We grow and eat a lot of kale in the winter. Usually we just steam it and scoff it down but it's good in soups too. Lots of recipes for Caldo Verde on the web, uses leeks normally, here's a version that just uses onions and we like it just as well:
Caldo Verde Onion Version
Boston Phoenix
ca. 1986; a Portuguese recipe
Serves four to six
1 large yellow onion, peeled and chopped fine
1 large garlic clove, peeled and minced
4 tablespoons (60 mL) olive oil
6 large potatoes
2 quarts (2 L) cold water
6 ounces (170 g) chorizo or similar [I like Silva linguia]
2 1/2 teaspoons (12.5 mL) salt (to taste - this is a lot of salt)
1/4 teaspoon (1 mL) pepper
1 lb (0.5 kg) kale
Saut the onion in !2TBS oil and add the garlic after onion is transparent and cook about a minute morel. Add potatoes and water, cover, and boil gently for 20 minutes until potatoes are soft, add kale and cook until tender. Fry the sausage in a skillet and drain. Add the sausage, salt and pepper to kale. Simmer 5 minutes. Serve with bread bread.
***I like it with less oil and we generally make it with no sausage and more garlic. Mash some of the potato chunks against the side of the pan to thicken the soup. Lots of pepper is good too.
****Edited to add: We grow Red Russian Kale, the flat leaf kind. If you use that, here's a tip: Don't bother to cut the rib/stalk out - hold a leaf upside down in one hand and with the other grip the leafy part between all your fingers and the edge of your hand, beginning at the top 'fins' start tearing downward, when you get into the main part of the leaf at some point the rib will break off. That part is tender enough to cook, do the other side. I can prepare a pound of kale in about 5 minutes, I don't even chop it - just tear it up and drop it into the collander.