2 Tbs fat-free mayonnaise
2 tsp Dijon mustard
1 can sliced mushrooms - (4 oz)
2 slices rye bread
4 oz thinly-sliced ham
1/2 red onion, thinly sliced
2 oz low-fat Swiss cheese, thinly sliced


Mix together the fat-free mayonnaise and Dijon mustard. Drain the canned mushrooms well (squeeze between paper towels).
Spread each slice of rye bread with the mayonnaise-mustard mixture. Set dry-side down on baking sheet. Top with mushrooms, ham, red onion, and the Swiss cheese.
Rather than frying, place the "open-faced sandwich" under a preheated broiler until the cheese is melted and slightly browned.