In a large skillet, melt butter over medium heat. Add diced onion and cook until translucent, about 5 minutes.
Add garlic and mushrooms. Sauté for another 3–4 minutes until mushrooms begin to soften.
Stir in canned deer meat and Worcestershire sauce. Cook for 2–3 minutes, just to warm through.
Pour in broth. If using flour to thicken, whisk it into the broth before adding. Simmer for 5–7 minutes.
Stir in sour cream. Cook gently over low heat, do not boil once sour cream is added.
Season with salt and pepper to taste.
Serve over hot egg noodles and garnish with fresh parsley if desired.