Grilled Zucchini Casserole with Mushrooms is an amazing summertime vegetarian comfort food. It’s layered with fresh produce and bursts with smoky, spicy and earthy flavors.
Prepare the zucchini: Slice about ½ inch off the ends off of the zucchini and then slice them thinly, about ¼ inch. The easiest way to do this is to use a mandoline. (If you don’t have one, use a Chef’s knife. First cut a base by slicing off a thin strip form one side. Then with the zucchini sitting steady of this base, cut it into thin slices.)
Grill the zucchini: Preheat a stove-top grill (or outdoor grill). On a baking sheet, generously coat the zucchini slices with olive oil and season them generously with salt and pepper. Once the grill is hot, add the zucchini slices — there should be about an inch between them. Grill until it's tender and nicely browned, about 2 minutes per side. Set aside on a baking sheet to cool.
Preheat the oven to 375°F.
Prepare the seasonings: In a small bowl, combine the jalapeño, garlic, chipotles in adobo and cumin. Set aside.
Sauté the vegetables: Coat a large sauté pan with olive oil and place it over medium heat. Add the onion and stirring often, cook until soft and golden, about 20 minutes. Add the seasoning mixture, stir, and cook until aromatic, about 30 seconds. Turn the heat to medium-high, drizzle with a bit more olive oil and add about half of the mushrooms. Stirring often, sauté until they’ve shrunk and softened, about 5 minutes. Add the second half of the mushrooms and continue to sauté until all of the mushrooms begin to brown, about 10 minutes. Mix in the beans and season to taste with salt and pepper. (Here’s How to Season to Taste.)
Assemble: Add an even layer of the grilled zucchini slices to the bottom of a 9 x 13 x 2 inch baking dish. Cover this with an even layer of about ⅓ of the mushroom-bean mixture. Sprinkle with ½ cup of the Mozzarella and ¼ cup of the Pepper Jack cheese. Repeat this layering process twice more — however, the top layer of cheese will be ¾ cup of the Mozzarella and ½ cup of the Pepper Jack.
Bake: Place the baking dish on a sheet pan and place in the preheated 375°F oven. Bake for 20 minutes. Remove from the oven and let it sit for about 15 minutes.
Garnish: After the 15 minutes of cooling time, garnish with the cilantro, avocado and jalapeño slices.