In LARGE non stick skillet, cook onions & bell until tender. Add mushrooms, eggs & rotel. Cook over med-low heat constantly stirring till eggs are done. Remove from heat, place cheese slices over top of eggs, place lid on top, let sit until cheese is melted.
Using a glass or cup, cut 6 rounds out of the eggs. Butter buns and place ham, egg & ham again.
Pop burgers in 400 degree oven for about 10 min. to toast buns.