Out of pure excitement, I have to share what I just had for dinner. This was totally improvised out of leftovers and I thought it wouldn't be very good, but it was actually amazing.
2 tbsp butter
1/4 tsp garlic
1/4 tsp italian seasoning
1/2 cap large portobello mushroom
2 slices wheat bread
1 tbsp mayonnaise
1 tsp brown mustard
Melt butter in small saucepan. Add spices; let simmer for a minute. Add portobello. Sautee for about 10 minutes, browning both sides. Toast the bread and dress with mayonnaise and mustard. Slice avocado and place on one slice of bread. Top with portobello and other slice of bread. Heaven!
The only real improvement I could see on this is to put it in a panini grill for a minute to finish it, but with the bread toasted it isn't really necessary. A variation could add some provolone, but again, it was great the way it was. Just had to share my happy accidental discovery!