Finely dice the onion, mince the garlic, grate the ginger, shred or julienne the carrot, finely chop the mushrooms, and thinly slice the green onions, keeping the white and green parts separate. In a small bowl, whisk together the gochujang, 2 tablespoons soy sauce or tamari, 1–2 tablespoons honey or maple syrup, 1 tablespoon rice vinegar, 1 tablespoon toasted sesame oil, 2–3 tablespoons water, 1 minced clove of garlic, 1 teaspoon grated ginger (if using), and 1–2 teaspoons sesame seeds until smooth and glossy. Adjust sweetness or thickness with more honey or water as desired and set aside.

Heat 1 tablespoon neutral oil in a large skillet over medium-high heat. Add the diced yellow onion and the white parts of the green onions and sauté for 3–4 minutes, until softened and translucent. Stir in the minced garlic and grated ginger and cook for about 30 seconds, just until fragrant.

Add the ground chicken (or your chosen protein) to the skillet. Cook for 5–7 minutes, breaking it up with a wooden spoon into small crumbles, until no longer pink and lightly browned in spots. If there is a lot of excess fat, carefully spoon some off.

Add the shredded carrot and chopped mushrooms to the skillet. Stir and cook for 3–4 minutes, until the vegetables soften and the mushrooms release their moisture. Pour in 2 tablespoons low-sodium soy sauce or tamari, 1 tablespoon rice vinegar, and 1 teaspoon toasted sesame oil. Toss to coat and reduce the heat to medium. The filling should be well-seasoned but not very saucy at this stage.

Stir the reserved gochujang sauce and pour about two-thirds of it over the filling in the skillet. Mix well so all the meat and vegetables are evenly coated. Let simmer for 2–3 minutes on medium heat until the sauce thickens slightly and clings to the filling. Taste and add more of the remaining sauce if you want extra heat or flavor, or reserve it for drizzling at the table. Stir in most of the green parts of the green onions, reserving some for garnish if desired, then remove the skillet from the heat.

While the filling cools slightly, gently separate the lettuce leaves, rinse them, and pat them very dry with a clean kitchen towel or paper towels. Arrange the dry lettuce leaves on a platter. Transfer the warm filling to a serving bowl and place it on the platter along with any remaining gochujang sauce, sesame seeds, extra sliced green onions, lime or lemon wedges, and cooked rice or cauliflower rice if using.

To eat, place a lettuce leaf in your hand and spoon a couple of tablespoons of the warm filling into the center. Drizzle with extra gochujang sauce if desired, then sprinkle with sesame seeds and sliced green onions and add a small squeeze of lime or lemon. Fold like a taco and enjoy immediately. Repeat with remaining lettuce and filling.