Using the same pan, melt butter over medium heat.
Add onions and cook until starting to soften, about 5 - 6 minutes. Add garlic, and stir to combine.
Add mushrooms, stirring to combine. Sauté mushrooms for 10 - 12 minutes, until they have started to cook down and release their liquid.
Sprinkle flour over the vegetables, stir to coat, making sure there are no pockets of flour. Add wine, if using.
Add dried thyme and rosemary, season with salt and pepper. Add chicken stock and stir to combine.
Add meatballs back into the sauce, and cover the pan. Reduce to medium-low heat and simmer meatballs for 15 minutes.
Remove from heat. Add cream and stir until fully incorporated. Serve with noodles, mashed potatoes, polenta or rice.