In a skillet, heat 1 tablespoon olive oil or butter until hot, reduce heat to medium and add 1/2 bunch scallions (or 1/2 of an onion), chopped. Cook until white parts start to become translucent. Add 1 bunch swiss chard or beet greens, stems trimmed and leaves roughly chopped. When greens have partially wilted, stir in 3 tablespoons dijon mustard and a little less than 1/4 cup half-and-half or whole milk. Continue cooking the greens until they are fully wilted and the sauce has thickened a bit. Add salt and fresh ground pepper to taste.