1Set oven control to broil. In 10-inch ovenproof nonstick skillet, heat oil over medium heat. Cook garlic and mushrooms in oil 4 minutes, stirring frequently, until mushrooms are tender. Add Swiss chard; cook 2 minutes or until just wilted. Reduce heat to medium-low.
2In medium bowl, beat eggs, whipping cream, salt and pepper until well blended. Pour over mushroom mixture. Cook 8 to 9 minutes, without stirring, until eggs are set around edge and beginning to brown on bottom (egg mixture will be uncooked on top). Sprinkle with cheese.
3Broil frittata with top about 5 inches from heat about 4 minutes or until eggs are cooked on top and light golden brown. (Frittata will puff up during broiling but will collapse when removed from broiler.) Cut into squares.