Clean the mushrooms and very finely chop, preferably using a food processor.

Heat the olive oil in a pan over medium heat and add the onions and mushrooms. Cook until mushrooms have browned and liquid has evaporated and onions are cooked down, about 10 minutes.

Remove from heat and stir in the garlic and stir for 20 seconds to incorporate.

Place the mushroom mixture into a large bowl and add the oats, cheese, bread crumbs, parsley, egg, salt, pepper and oregano. Mix together with a spoon until mixture comes together; it should hold together when pressed. Place in the fridge and allow to rest for 30 minutes.

When ready to bake, preheat the oven to 450 degrees F and line a baking sheet with a silicone baking mat (like a silpat) or parchment paper. Form meatballs into small balls, using a 1 tablespoon scoop. Roll meatballs between hands to form a smooth ball, then place on the prepared baking sheet.

Repeat for the rest of the meatballs, then drizzle with olive oil. Bake for 15 minutes until golden brown; flipping halfway through baking time.

While the mushrooms are cooking, prepare the rest of the sauce. Bring a large pot of salted water to a boil. Once boiling, add the egg noodles and cook until al dente according to package directions.

Heat a large skillet over medium-high heat. Add 1 tablespoon of oil and the onion and saute until onion is soft, about 6 minutes. Add the garlic and mushrooms and cook until mushrooms are browned and cooked down, about 10 more minutes.

Add the remaining tablespoon of oil along with the flour and cook for about 2 minutes until mixture is lightly browned.

Stir in the broth, mustard, thyme and salt and stir, until mixture thickens, about 3 minutes. Add in the meatballs and simmer for an additional 10 minutes.

Remove mixture from heat and stir in the yogurt until just warmed through.

Serve over hot cooked egg noodles and garnish with parsley.