This slow cooker Amish mustard beef is the kind of low-effort dinner that feels like a little win on a busy day. A brisket flat gets coated with yellow mustard and cooked low and slow with just a few pantry staples until it turns tender, savory, and full of old-fashioned comfort. It has that simple, hearty style often associated with Amish home cooking, where straightforward ingredients come together into something especially satisfying.
Serve this beef with buttery mashed potatoes, egg noodles, or steamed rice to catch all of the rich sauce. It also pairs well with roasted carrots, green beans, buttered corn, or a crisp side salad if you want to balance the meal with something fresh. Leftovers are excellent piled onto sandwich rolls or spooned over toasted bread for an easy lunch the next day.
Slow Cooker 5-Ingredient Amish Mustard Beef
Servings: 6
Ingredients
2 1/2 to 3 pounds beef brisket flat
1/2 cup yellow mustard
1 packet onion soup mix
1 cup water
2 tablespoons cornstarch
Directions
1. Place the beef brisket flat into the slow cooker, fat side up if it has a fat cap. Spread the yellow mustard all over the top and sides of the brisket.
2. Sprinkle the onion soup mix evenly over the mustard-coated brisket, then pour the water around the sides of the meat so the seasoning stays mostly on top.
3. Cover and cook on low for 8 to 9 hours or on high for 4 1/2 to 5 1/2 hours, until the brisket is fork-tender.
4. Transfer the brisket to a cutting board and let it rest for 10 minutes. Skim excess fat from the cooking liquid if needed. Whisk the cornstarch with 2 tablespoons of cold water in a small bowl, then stir it into the slow cooker liquid. Cover and cook on high for 10 to 15 minutes, until the sauce thickens.
5. Slice the brisket against the grain or shred it into large pieces, then return it to the thickened sauce or spoon the sauce over the top before serving.
Variations & Tips
Add vegetables: If you want this to be more of a full one-pot meal, tuck in chunks of carrots, potatoes, or onion around the brisket during the last few hours of cooking. They soak up the savory sauce and make dinner even easier.
Make it ahead: This is a great prep-night recipe. You can mustard the brisket and add the soup mix to the slow cooker insert the night before, cover it, and refrigerate. The next morning, add the water, set the insert in the cooker, and start cooking.
Adjust the sauce: For a looser, more spoonable sauce, use just 1 tablespoon of cornstarch. If you like a thicker gravy for serving over potatoes or noodles, keep the full 2 tablespoons and let it cook until nicely glossy.
Use leftovers well: Leftover beef reheats beautifully with a splash of the sauce. Try it in sandwiches, over buttered egg noodles, or tucked into a baked potato for an easy second meal.
Slicing tip: Brisket is easiest to slice neatly after a short rest. Always cut against the grain so each piece stays tender instead of chewy.