In a food processor, pulse the mushrooms and green onions until they are finely diced. Add the remaining meatball ingredients and pulse until combined.

In a large skillet or dutch oven, warm the oil over medium heat. Scoop the meatball mixture in balls in a single layer onto the skillet (I used a little cookie scoop, but you could just dump them in little piles with a spoon, if you'd prefer).

Let them cook until the bottoms have browned, about 3-5 minutes. Flip them over and let the other side cook until browned. They don't need to be cooked all the way through.

With a spatula remove all the meatballs from the pan and put on a plate. Set aside.

Add more oil if needed (I added about 1 Tablespoon more) and stir in onions and garlic. Cook about 3 minutes. Stir in the coconut milk and green curry paste, scraping the bottom of the pan to pull up any browned bits. Cook about 3 minutes, stirring frequently.

In a small bowl, whisk together the cornstarch and water. Pour slowly into the sauce, whisking to combine.

Add the meatballs back to the sauce and let cook until the sauce comes to a boil and meatballs are cooked through. Salt to taste.

Serve over rice.