Cook the quinoa: Preheat the oven to 400 degrees. In a small pot, bring 1 1/2 cups of water, the stock concentrate, and a large pinch of salt to a boil. Once boiling, add the quinoa, cover, and reduce to a simmer for about 15 minutes, until tender.

Prep the ingredients: Halve, peel, and finely chop the shallot. Mince the garlic. Finely chop the parsley. Slice the mushrooms. Halve the bell peppers lengthwise and remove the core, seeds, and white ribs.

Roast the peppers: Drizzle the peppers with olive oil and season with salt and pepper. Roast for 10-12 minutes, until slightly softened.

Heat 1 Tablespoon oil in a large pan over medium-high heat. Add the mushrooms and cook, tossing, for 4-5 minutes, until golden brown. Add the shallot and garlic and cook for 2-3 minutes, until fragrant.

Add 1 Tablespoon vinegar, the soy sauce, quinoa, half the pepitas, and half the parsley to the pan. Cook, tossing, for 1 minute.

Stuff the peppers: Spoon the quinoa into the peppers and bake for 5-7 minutes, until the peppers are softened.

Sprinkle the stuffed peppers with the remaining parsley, pepitas, and the feta cheese. Enjoy!