Cut tomatoes into cubes and drain in a colander for several minutes.
Meanwhile, in a 10 to 11-inch frying pan over medium-high heat, cook mushrooms in butter, stirring, until mushrooms are soft and juices have evaporated.
Add tomatoes and stir to heat through.
Reduce heat to low.
With a spoon make 6 or 8 depressions in mushroom-tomato mixture; break an egg into each depression.
Sprinkle with salt and pepper and cover evenly with cheese.
Cover pan and cook over low heat until eggs are set as you like and cheese is melted.
Garnish with parsley