Serve the Amish butter beef tips hot, spooning both the meat and plenty of the buttery pan juices over your chosen side. Store any leftovers in an airtight container in the refrigerator for up to 3 days; reheat gently on the stovetop or in the microwave with a splash of broth if needed.
For a creamier version, stir in 1/2 cup of sour cream or heavy cream during the last 15 minutes of cooking, just until warmed through—this gives the sauce a stroganoff-like richness. If you prefer a thicker gravy, whisk 1 tablespoon cornstarch with 2 tablespoons cold water, then stir the slurry into the slow cooker during the final 20 to 30 minutes on HIGH, letting it bubble until slightly thickened. To add a bit of freshness without complicating the ingredient list, finish with a small handful of chopped fresh parsley right before serving. You can also swap the onion soup mix for a garlic-herb soup mix for a different flavor profile, or use a mix of beef tips and mushrooms (about 8 ounces of button or cremini mushrooms, halved) for extra savoriness. If you need to stretch the meal, serve the butter beef in toasted sandwich rolls for an easy, French dip–style sandwich, using the cooking juices as a dipping sauce.