Place broccoli in a pan and cover with water. Bring to a boil over high heat. Reduce heat and simmer at a low boil for about 2 minutes or till just barely fork tender. Remove from heat. Drain water from pan and rinse broccoli in very cold water. Drain and set aside. This can be done the day ahead. Refrigerate cooked broccoli until ready to assemble breakfast bake.
Heat oven to 350° degrees. Spray bottom only of 13" x 9" glass baking dish with cooking spray. Separate dough into 5 biscuits. Cut each biscuit into 8 pieces; arrange evenly in sprayed dish.
Melt butter over medium heat in a medium saute pan. Cook the onions and mushrooms until mushrooms have released their liquid and onions have softened. Season with salt to taste. Remove pan from heat and set aside.
In large bowl, beat eggs, milk, mustard, salt and pepper with wire whisk until well blended. Stir in cooked broccoli, cooked chopped bacon, cooked onion and mushrooms, both cheeses, salt and pepper to taste. Pour mixture over biscuit pieces in dish. Press down with back of spoon, making sure all biscuit pieces are covered with egg mixture. Sprinkle top of casserole with chopped thyme.
Bake at 350°F. for 40 minutes or until edges are deep golden brown and center is set. Let stand 10 minutes before serving. Cut into squares.