Wilted beet greens

1 Tbsp olive oil
1/4 cup chopped onion
1-2 Tbsp butter
1/2 tsp crushed rosemary leaves
Beet greens or Swiss chard washed well and chopped (stems chopped separately from leaves).
1 tbsp Balsamic vinegar or to taste
Coarse salt (Kosher or sea salt) and freshly ground peper

Wash greens well and don’t dry them. Chop stems of greens separated from leaves. Over low or medium-low heat in 12″ saute pay, saute onion and stems from greens in olive oil until soft. Add butter and melt. Add rosemary and heat for 30-60 seconds or until fragrant. Add chopped leaves from greens and cover until wilted. Season with salt and pepper and serve immediately.