Beet (or other) Greens with Caramelized Onions

Pretty much exactly how it sounds. Slightly sweet and delicious.

2 onions, sliced thinly
2 cloves garlic, minced
1 small bundle dark leafy greens (I used beet greens, but am sure it would also work with kale or other greens), washed and cut into ribbons.
a handful of chopped walnuts (optional)

Heat a small amount of oil in a wide saute pan over medium heat. Add the onions and stir fairly constantly until they begin to turn golden brown (about 5-10 minutes). Turn the heat down to medium-low and continue to cook, stirring fairly constantly, until they're very brown and smell sweet and delicious. Add the garlic; cook for about 1 minute. Add the greens and cook just until wilted. Add salt and pepper to taste, and toss in walnuts if using.