1. Prepare mushrooms: once mushrooms and onions are sliced and ready to go, heat a nonstick pan on medium heat. Add oil and onions with a pinch of salt, and sautée for 2-3 mins until they begin to soften. Then add mushrooms (and garlic if desired) and another pinch of salt. Stir every couple of minutes. You're looking for the mushrooms to release their water. 

2. Add soy sauce/tamari/coconut aminos: once the mushrooms release their juices, and their volume has reduced by at least half, it's time to start thinking about adding flavor back in. Let the water evaporate - once the mushrooms start sticking to the pan a little, add soy sauce. Let most of the soy sauce evaporate, then transfer to dish to cool. 

3. Put together quesadillas: using the same pan as the previous step (it's already seasoned, don't let those flavors to go waste!), set the heat to low-medium. Lay down a tortilla. On one half of the tortilla, put down a thin layer of cheddar shreds. Then add a few tsp size pieces of mozzarella. Using a slotted spoon, lay down a thin layer of mushrooms, and top with sliced jalapeno. Fold the empty half over, and cover pan for 2-3 minutes. Then flip. The tortilla should have a little crispiness, but isn't burnt. Cover for another 2-3 minutes, then remove from pan, slice, and enjoy with pico and sour cream.