Place the lentils into a small saucepan with 3 cups of water. Place over high heat and bring to a boil. Lower heat and allow to simmer, uncovered, for about 25 minutes, until the lentils are just shy of being fully cooked and still a tiny bit firm at their centers. Add water to the pot during cooking if it all dries up. Once finished cooking, drain any excess water and set the lentils aside to coll while you prep the remaining ingredients.

Place the lentils into a large mixing bowl. Add the onion, garlic, walnut, ½ cup panko, vinegar, cumin, ancho chili powder, cayenne, salt, and pepper. Dig in with your hands and mix everything up. Test the mixture by pressing some together in your hands. If it seems too squishy and doesn't hold together, add a bit more panko and try mashing a small portion of the lentils with a fork.

Lightly oil the bottom of a large nonstick skillet and place it over medium heat. Shape the mixture into 4 to 6 patties, transferring each directly to the skillet after shaping. Avoid crowding the skillet, and work in batches if needed, adding oil to the skillet as needed between batches. Cook each patty until browned on the bottom, about 4 to 5 minutes. Carefully flip and cook 4 to 5 minutes more, until browned on the other side.

Whisk all ingredients together in a small bowl, thinning with as much milk as is needed. Taste test and adjust seasonings if needed.

Stuff the burgers into buns, and top with tahini nacho cheese and toppings of choice. Serve.