Now here's a meal whose GBD quotient is through the roof. That's "golden brown deliciousness," of course! Gloriously melty mozzarella is sandwiched between meaty portobello mushrooms, then (are you sitting down?) the whole thing is breaded in crispy panko and fried to golden perfection. Enjoy with oven roasted sweet potato cottage fries for a veggie burger that makes no apologies.
Cut sweet potato into ¼" slices. Slice Roma tomato into six ¼" rounds. Using a spoon, scoop out black undersides (gills) of portobello mushrooms. Place sweet potato slices on baking sheet, drizzle with olive oil, and season with ¼ tsp. salt and a pinch of pepper. Roast in oven 20 minutes, or until tender and deep golden.
Micro-Steam the Portobellos
Line a plate with two paper towels. Place 2 portobellos on plate, cover with two more pieces of paper towel, and top with another plate (plates are used as a weight and should be facing the same direction). Microwave for 4 minutes. Portobellos should be flat and juices mostly absorbed by paper towels. Repeat with other 2 portobellos, adding fresh paper towels for each batch. Let portobellos cool until you can safely handle them, about 2 minutes.
Make the Burgers
Divide mozzarella in half. Using your hands, press half the mozzarella into a ball. Twist cheese tightly in plastic wrap if you're having trouble here. Repeat with second half. Flatten each ball into a puck and place pucks on top of the gill side of 2 portobellos. Top with remaining portobellos (gill side down), wrap each individually and tightly with plastic wrap, and press with your hands to form burgers.
Bread the Burgers
Heat canola oil in a small pot over medium heat. Set up a breading station by placing liquid eggs and panko into separate small bowls. Dip portobello burger into egg, then into panko. Dip in egg again, and then in panko again. Repeat with remaining burger. Use extra panko moistened with egg to patch any "holes" in breading.
Cook the Burgers
Test oil temperature by adding a pinch of panko to pot. It should sizzle gently. If it browns immediately, turn heat down and let oil cool. If it doesn't brown, increase heat. Add one burger to oil and fry 4-5 minutes per side, or until golden brown. Remove to a paper towel-lined plate and sprinkle each side with ¼ tsp. salt. Repeat with second burger.
Plate the Dish
Place tomato and arugula on bun, place portobello burger on top, and top with remaining bun. Serve next to cottage fries. Be careful when biting into burger - cheese will be hot!