Prep the vegetables: Finely dice 1 medium onion and 1 green bell pepper. Clean and finely chop 12 ounces of cremini mushrooms. Mince 3–4 cloves of garlic. Rinse 1 cup of dry brown or green lentils.

Sauté the aromatics: Heat 2 tablespoons of oil in a large skillet or Dutch oven over medium heat. Add the onion and bell pepper with a pinch of salt. Cook 5–6 minutes until softened and lightly golden.

Add mushrooms and garlic: Stir in the mushrooms. Cook 6–8 minutes, stirring occasionally, until they release moisture and it evaporates. Add the garlic and cook 30 seconds until fragrant.

Bloom the spices: Sprinkle in 1 teaspoon smoked paprika, 1 teaspoon chili powder, and 1/2 teaspoon ground cumin. Stir for 30 seconds to toast the spices.

Build the sauce: Add 1 cup tomato sauce, 2 tablespoons tomato paste, 1 tablespoon Dijon or yellow mustard, 1 tablespoon brown sugar (or 1–2 teaspoons maple syrup), 1 tablespoon Worcestershire, and 1 tablespoon apple cider vinegar. Stir well.

Add lentils and liquid: Stir in the rinsed lentils and 2 1/2 cups vegetable broth. Bring to a simmer, then reduce heat to medium-low. Cover partially and cook 25–30 minutes, stirring occasionally, until lentils are tender but not mushy. If it becomes too thick, add a splash of broth; if too thin, simmer uncovered to reduce.

Season to taste: Add 1/2–3/4 teaspoon salt and several grinds of black pepper. Taste and adjust sweetness, acidity, and heat. Add a pinch of red pepper flakes or a few dashes of hot sauce if you like.

Toast the buns: Split the buns and toast them in a dry skillet or under the broiler until lightly crisp. This helps them hold up to the saucy filling.

Assemble: Spoon a generous amount of the mushroom-lentil mixture onto each bun. Top with pickles, sliced onions, or slaw if you like. Serve warm with napkins close by.