1. Wash the vegetables. Slice the tomatoes and mushrooms.
2. Slice the mozzarella cheese thinly.
3. Heat a little olive oil in a pan. Over high heat, add the tomatoes and cook them lightly (about a minute, stirring), with a little garlic powder and Provence herbs.
4. Set aside the tomatoes.
5. In the same pan, sauté the mushrooms. Season with salt and pepper, then set them aside.
6. Lightly spread one side of a slice of bread with sour cream (don't use too much! It's just to prevent the bread from drying out during cooking). On top, stack in the following order:
7. A small layer of grated gruyère cheese.
8. Half a slice of ham.
9. A layer of mushrooms.
10. A layer of garlic tomatoes.
11. Mozzarella cheese (one or more slices, depending on your taste).
12. Then, spread sour cream on both sides of another slice of bread and place it on top; finally, sprinkle a little gruyère cheese on top of the croque-monsieur.
13. Repeat the process to make 8 croque-monsieurs, then bake in a hot oven (350°F) for 10 minutes.
14. Broil, keeping an eye on them, until your croque-monsieurs are nicely golden.
15. When they come out of the oven, cut them in half diagonally; serve them half by half, leaving the rest in the oven while you eat (300°F) because the mozzarella cools quickly and it's less tasty that way.
16. I serve them with a green salad with bacon.