Quesalipie is the name I gave to these cheesy, vegetable and green filled leeks. Starting from the quesadilla recipe I used Lebanese leeks instead of tortillas. For cheese I used, telema and mozzarella, but I also use cheddar, gorgonzola, roquefort, stilton when I have. The more kinds of cheese, the better it is. The vegetables cut into small cubes and the grated, seasoned cheese I put into loose glue like a pocket.
For meat I used slices of prepared pork tenderloin that I keep in the freezer. Instead of sausages and pre-packaged meats, I prefer to buy a piece of pork tenderloin which I cook whole in the oven, leave it to cool in the fridge so whole and the next day I cut it into thin slices and put it in the freezer. Either use them for sandwiches or in dishes that "call" for a little meat, like quesadillas.
Of course they are just as good without meat.
You can fill the leeks with any vegetables, meat and greens you like. But be careful not to choose any ingredients that leave a scum. If you want to use mushrooms, my recommendation is to sauté them before putting them in the cheese mixture because otherwise they will leave a lot of juice when you put them in the oven.