In a large skillet over medium high heat, brown 1 pound ground beef along with ½ cup diced yellow onion, and 1 teaspoon minced garlic until thoroughly cooked and crumbled.
Drain ground beef to remove excess grease from pan. Put pan back on stove over medium heat (don't add the ground beef back in yet.) Add 3 Tablespoons salted butter and allow it to melt.
Then add 3 Tablespoons all purpose flour to the pan, whisk and let it absorb butter.
Add 1 ½ cups beef broth and whisk vigorously to remove any lumps, turning the heat up to high, bringing it to a boil for 2-3 minutes until you see it thicken slightly.
Bring temperature down to medium and whisk in 1 cup sour cream and 10.5 ounce can cream of mushroom soup. Stir until mixture is thoroughly incorporated.
Add salt and pepper, to taste. Keep tasting mixture until it is seasoned the way you like. If it gets too thick, just add a tad more beef broth.
Add ground beef back to mixture until reheated.
Serve over cooked egg noodles and enjoy!