Melt butter in microwave, about 40 seconds. Place egg yolks, warm water, lemon juice and salt in blender. Blend on high. With the blender running, carefully remove the top and very slowly add melted butter to egg mixture. The mixture will thicken. Poach 4 eggs and set aside.
2. Eggs Benedict
Turn oven to broil. Cook bacon in skillet and set aside. Brush mushrooms on both sides with oil and place gill side down on a large, broiler plate and cook for about 3 minutes. Turn the mushrooms gill side up; add bacon on each mushroom, place back in broiler for 2 minutes or until fully heated and crisp.
To serve, place mushroom on plate gill side up, pat with paper towel to remove moisture. Top with a poached egg and 2 tablespoons of hollandaise. Serve immediately.