roasted portobello sandwich

START: Preheat your oven to 425°F (to roast mushroom caps, sweet potatoes and to toast bread). Start prepping when your oven comes up to temperature!

ROAST SWEET POTATOES: Wash and dry all produce. Cut sweet potatoes into 1/4-inch matchstick fries. On a parchment-lined baking sheet, toss potatoes with 1 tbsp oil. Season with salt and pepper. Roast in middle of oven, turning halfway through cooking, until golden-brown, 20-22 min.

CARAMELIZE ONIONS: While sweet potatoes roast, heat a large non-stick pan over medium heat. When hot, add 1 tbsp oil, then onions. Cook, stirring occasionally, until softened, 3-4 min. Add 1 tsp sugar and season with salt. Cook, stirring occasionally, until dark golden-brown, 10-11 min.

ROAST MUSHROOMS: While onions cook, pull the stems off mushroom caps. Brush the inside and outside of mushroom caps with 1 tsp oil. Season with salt and pepper. Arrange caps top-side up on another parchment-lined baking sheet. Bake, in middle of oven, until juicy and fork-tender, 10-12 min.

PREP AND FINISH ONIONS: While mushrooms bake, thinly slice tomatoes. In a small bowl, mix mayo and pesto. Set aside. When onions are done, add 1 tbsp vinegar. Stir together until absorbed and onions are glossy, 1-2 min. Remove the pan from heat and transfer onions to another small bowl. Set aside.

TOAST BUNS AND FINISH MUSHROOMS: When mushrooms are fork-tender, flip the caps over and fill with cheese. Halve buns, then arrange, cut-side up, on the same baking sheet. Toast in middle of oven, until buns are golden-brown and cheese melts, 3-4 min.

FINISH AND SERVE: Spread pesto aioli on top buns. Layer each bottom bun with mushroom cap, onions and tomatoes. Top with top bun. Divide sandwiches and sweet potatoes between plates. Serve any remaining pesto aioli on the side, for dipping.