Preheat oven to 375°.
Melt butter in a large saucepan over medium heat. Add onion and garlic; cook 5 minutes or until golden, stirring occasionally. Stir in broth, milk, and salt; bring to a boil. Gradually add grits, stirring constantly with a whisk; simmer 5 minutes, stirring frequently. Remove pan from heat; stir in cheese, egg substitute, and pepper. Spoon grits mixture into an 11 x 7-inch baking dish coated with cooking spray. Bake at 375° for 40 minutes.