In a small bowl, combine the pea crumbles with ½ cup hot water. Set aside and allow them to rehydrate.
In a food processor, add the mushrooms and garlic. Process until finely chopped. I used a mini processor and processed the mushrooms in two batches.
In a large pot or skillet, warm the oil over medium-low heat. Add the finely chopped mushrooms and garlic. Cook, while stirring intermittently, until the mushrooms release their liquid.
To the skillet, add the rehydrated pea crumbles, 4 tablespoons reduced sodium tamari, 2 tablespoons tomato paste, 1 tablespoon pure maple syrup, 1 teaspoon vegan Worcestershire sauce, 2 teaspoons Italian seasoning, 1 teaspoon onion powder, and 1 teaspoon smoked paprika. Stir to combine and continue to cook for 5 minutes more. Remove from heat and set aside.
In a food processor, add the sunflower seeds and process until finely chopped. Add ½ of the lentils (on top of the sunflower seeds) and process again until the lentils are finely chopped.
In a large bowl, add the finely chopped sunflower/lentil mixture, the remaining whole lentils, and the mushroom mixture from the skillet. In a small bowl, whisk the egg then add to the large bowl. Sprinkle 1 tablespoon nutritional yeast and ¼ cup chickpea flour over top. Stir together until evenly combined.
Scoop out about ¼ cup of the sausage mixture at a time and shape into patties. (If the mixture feels too wet to work with, you can refrigerate it for 15-20 minutes to help it firm up.) I like to use a silicone mold to shape them but you can also shape them by hand. Transfer patties to a parchment lined baking sheet. Bake at 375°F for about 8-10 minutes on each side. They will be delicate to handle when flipping but will firm up after they are completely cooked and cooled.
Once they have cooled completely, transfer to an airtight container and refrigerate for up to 1 week or freeze for up to 3 months.