Swiss Chard with Onions & Garlic

Ingredients (8)

• 2 tablespoons olive oil
• 2 medium onions, chopped
• 6 garlic cloves, sliced
• 1/2 cup white balsamic vinegar
• 2 bunches Swiss chard, coarsely chopped (about 16 cups)
• 1/2 cup walnut halves, toasted
• 1/4 teaspoon salt
• 1/4 teaspoon pepper