|6 tbsp||white wine vinegar|
|6 tbsp||olive oil (divided)|
|1 tsp||dried oregano|
|30 g||pine nuts|
|120 g||jarred sun-dried tomatoes|
|1||red bell pepper|
Clean portobello mushrooms, if needed. Remove stems with a paring knife and lay the mushrooms skin-side down in a baking dish. Peel and mince garlic, and add to a bowl with white wine vinegar, a portion of the olive oil, honey, oregano, salt, and pepper. Mix well to combine. Pour mixture over the mushrooms and let marinate for approx. 1 hr. in the fridge.
Meanwhile, toast pine nuts in a frying pan and set aside in a bowl. Pluck basil leaves from the stem and place in food processor. Add drained sun-dried tomatoes, toasted pine nuts, a portion of the olive oil, salt, and pepper. Blend to a paste and set pesto aside.
Slice mozzarella. Wash bell pepper and remove the end and the entire inner, then slice into rings. Peel and halve onions. Halve avocado and remove the pit. Scoop out the flesh and slice. Heat the remaining olive oil in the same frying pan used to toast the pine nuts over medium-high heat and sauté onions for approx. 2 min. Sprinkle with sugar and let caramelize for approx. 2 min. more. Season with salt and toss.
Heat grill pan over medium-high heat and toast burger buns. Remove from pan and set aside. Place mushrooms skin-side up in the pan and sear for approx. 2 min. Flip, and place mozzarella slices on top. Fry for approx. 2 min. more.