In a medium skillet over medium-low heat, cook the onions, olive oil, salt, pepper and thyme until translucent (about 10 minutes). Add Worcestershire sauce, chicken broth, and tomato paste. Mix well, and cool to room temperature.
1 large sweet onion, 1 tablespoon olive oil, 1 teaspoon salt, ½ teaspoon pepper, ½ teaspoon fresh thyme leaves, 3 tablespoons Worcestershire sauce, 1/3 cup chicken broth, 1 teaspoon tomato paste