Deglaze the skillet with the red wine (if using), scraping up any browned bits from the bottom. Pour the wine mixture into the crockpot.
Add the beef broth, Worcestershire sauce, and dried thyme to the crockpot. Stir gently to combine.
Step 4: Slow Cook
Cover the crockpot and cook on low for 6–8 hours or high for 3–4 hours , until the beef is tender and the flavors have melded together.
Step 5: Add the Creamy Sauce
During the last 30 minutes of cooking, stir in the cream of mushroom soup and heavy cream.
Mix the cornstarch slurry into the sauce to thicken it slightly. Continue cooking until the sauce has thickened and heated through.
Step 6: Serve and Enjoy
Garnish with fresh parsley if desired, and serve the beef tips and mushrooms over cooked rice, mashed potatoes, egg noodles, or polenta. Enjoy the rich, creamy goodness!