Pre-heat the oven to 400 F (if preparing the day before, skip this step).
Chop the mushrooms, carrot, onion, and apple (very fine).
Add water and salt to a saucepan and add the lentils. Bring everything to a boil, then cover the pot with a lid, reduce the heat, and let the lentils simmer until soft (35-40 minutes). Strain off the excess water when finished.
Pre-heat a skillet over medium-high. Add avocado oil and allow it to warm for a few seconds. Then add the mushrooms to the skillet (it will look like a lot of mushrooms). Sautee until the moisture is gone from the mushrooms and the mushrooms are beginning to brown (20-30 minutes). Transfer the mushrooms to a bowl and set aside for later.
Re-heat the skillet over medium-high heat. Add 1 teaspoon more avocado oil. Sautee carrots, onions, rosemary, and thyme until the vegetables are tender and caramelized (20 minutes). Then add the chopped spinach and sautee another couple minutes until soft and wilted.
In a medium bowl, combine all the meatball ingredients (diced apple; cooked lentils; sauteed mushrooms; sauteed carrot, onion, and spinach mixture; nutmeg; allspice; ginger; mustard, apple cider vinegar; and coconut aminos). Mix well. If preparing ahead of time, cover the mixture and place it in the fridge overnight.
Form the dough into 20 balls of 2-3 Tablespoons each, and place them on a baking sheet.
Bake the meatballs for 25 minutes. Then flip the balls and bake for another 15 minutes. Then toss the balls with extra virgin olive oil and set them aside while you make the cream sauce.
Make a slurry of 2 Tablespoons potato starch and 1/4 cup of the cold oat milk.
In a skillet, combine all the remaining sauce ingredients (remaining oat milk, coconut aminos, cracked pepper, whole grain mustard, molasses, and thyme) and whisk together until combined. Simmer for 5 minutes. Then nestle the meatballs into the sauce and simmer for another 10-15 minutes or until everything is nice and warm. Serve warm and enjoy!!