Holding each pepper upright, slice approximately one third of the pepper off lengthwise. Remove seeds and web from the peppers and place the sliced off pieces aside.
Place the peppers cut side down on a parchment-lined baking sheet and bake for 25 minutes at 375ºF to soften flesh. Remove from oven and cool completely.
Place rinsed quinoa into vegetable broth in a small saucepan and bring to a boil. Cover and reduce heat to simmer for 10 minutes before removing from heat. Let sit covered for 5 to 10 minutes before removing lid and fluffing with fork. Set aside.
While quinoa is cooking, place rinsed lentils into a pot of water and bring to a boil. Cover and reduce heat to simmer for 20 to 30 minutes until lentils are tender. Drain and set aside.
Mash half of the beans and place in a bowl with the remaining beans and cooked quinoa and lentils. Set aside.
Heat oil in a large pot and sauté onion, celery, mixed peppers, jalapeño pepper and garlic until vegetables are tender (approximately 5 to 7 minutes), seasoning with salt and pepper. Add diced mushrooms and Worcestershire sauce and continue to sauté until mushrooms have released their moisture (approximately 5 minutes).
Reduce heat to medium low and add smoked paprika, oregano, cumin, tomato paste and corn, stirring to combine and release flavour. Remove from heat after 1 to 2 minutes.
Combine vegetable mixture with the quinoa, lentils and beans and mix thoroughly.
Stuff peppers with mixture and place on a parchment-lined baking sheet. Bake at 350ºF for 40 minutes or until heated through.
Garnish with sliced avocado and vegan sour cream and serve with your favourite relish! Enjoy!