Preheat oven to 350 degrees, line a baking sheet with a silicone mat.
Saute mushrooms, 1.5 cups kale, onion, and garlic with veggie broth until soft and the liquid has evaporated. Set aside to cool enough to be transferred into the food processor.
Transfer to a food processor. Add lentils, oats, almond flour, sunflower seeds, oregano, smoked paprika, salt and pepper in the food processor and pulse lightly until crumbly. Be careful not to overdo it.
Let sit for about 5-10 minutes so the oats can soak in some liquid (you can also do this after you shape into balls as well).
Shape into 2-inch balls and place on the baking sheet. Bake for 25 minutes, flip and bake 10 more minutes until they are browned on top.
While the meatballs are baking, saute 2 cups of kale and garlic in a pan with veggie broth until wilted. Add marinara and heat through.
Toast the buns in a toaster or in the oven for 5 minutes.
To serve, placing 3 meatballs in each bun and top with marinara mixture.