garlic
onions
yellow squash
zucchini
mustard greens
olive oil
opt:  chicken broth
salt, pepper

Saute the onions and garlic in a bit of olive oil. Once they start to become either translucent or to carmelize (depending on what sort of flavour you prefer), add butter and chopped up squash/zucchini.  Spice to taste (this is also where you add the broth if you want to.)  While those are sauteing, tear up the mustard greens into appropriate bits.  Once the squash and zucchini are cooked but not soggy, toss in the greens, stir near constantly until the greens are cooked to your preference.  Just barely wilted works here.
Simple, wonderfully tasty, and most of it was from our garden.