Cowboy Butter Portobello Sirloin Tips: Easy Crockpot Dinner Tips, FAQ & printable recipe

Tips for success

For the best texture, choose sirloin tips that have some marbling—this keeps them moist during the long cook. If you can only find lean tips, consider adding a tablespoon of olive oil or an extra pat of butter to compensate.

Slice the mushrooms thickly so they don't turn to mush; they should retain a slight bite even after hours of cooking. And don't skip the shallots—they melt into sweet, savory nuggets that are as delicious as the beef.

If you want a thicker gravy, remove the meat and vegetables from the slow cooker with a slotted spoon, then whisk 2 tablespoons of cornstarch with 2 tablespoons of cold water and stir it into the hot liquid.

Cook on high for 10 minutes until thickened. Taste and adjust seasoning with salt and pepper, but remember that the au jus mix is already salty. For a brighter finish, a sprinkle of fresh parsley just before serving adds color and freshness.

Variations

• Add Bacon: Cook 4 slices of bacon until crisp, crumble, and stir into the slow cooker during the last hour of cooking. The smoky flavor pairs beautifully with the beef and mushrooms. Or use the bacon fat to sear the beef first for extra depth.
• Spicy Kick: Add 1 teaspoon of red pepper flakes or a minced jalapeño along with the au jus mix. The heat will mellow during the long cook, leaving a subtle warmth. For more heat, serve with a drizzle of hot sauce or a sprinkle of cayenne.
• Vegetable Boost: Add 2 large carrots, cut into 2-inch chunks, and 2 celery stalks, sliced, along with the mushrooms and shallots. The vegetables will soften and sweeten, adding more body to the gravy. You can also add baby potatoes for a heartier meal.
• Herb Swap: Instead of garlic-herb cowboy butter, use a rosemary-garlic butter or a compound butter with fresh sage and thyme. If you don't have compound butter, mix 4 tablespoons of softened butter with 2 minced garlic cloves and 1 teaspoon of dried rosemary.

Storage and make-ahead

Fridge

Store in an airtight container in the refrigerator for up to 4 days. Reheat gently on the stovetop or microwave, adding a splash of broth if needed.

Freezer

Freeze in a freezer-safe container for up to 3 months. Thaw overnight in the refrigerator before reheating.

Reheat

Reheat in a saucepan over medium-low heat, stirring occasionally, until hot and bubbly.

Store leftovers in an airtight container in the refrigerator for up to 4 days. The flavors will continue to meld, and the gravy will thicken as it cools.

Reheat gently on the stovetop or in the microwave, adding a splash of beef broth or water if needed to loosen the sauce. The beef may become even more tender on reheating, which is a bonus.

This recipe is ideal for meal prep. Assemble all the ingredients in the slow cooker insert the night before, cover, and refrigerate. In the morning, place the insert in the slow cooker and cook as directed.

You can also cook the full dish, cool it completely, and refrigerate for up to 3 days before reheating. The flavors only improve with time.

Serving ideas

The classic way to serve this is over creamy mashed potatoes, as shown in the video. The potatoes soak up the rich garlic-butter au jus, making every bite comforting and satisfying. For a lower-starch option, serve over cauliflower mash or buttery egg noodles. A side of crusty bread is perfect for dipping into the remaining gravy.

For a complete meal, add a simple green salad with a tangy vinaigrette to cut through the richness. Roasted green beans or asparagus also pair well. If you have leftovers, shred the beef and use it as a filling for sandwiches or tacos—the gravy acts as a built-in sauce. Garnish with fresh thyme or parsley for a pop of color.

Frequently asked questions

Recipe card

Cowboy Butter Portobello Sirloin Tips: Easy Crockpot Dinner

Prep 10 minCook 6 hTotal 6 h 10 minServes 6

Ingredients

• 2 lb top sirloin steak tips
• 8 oz portobello mushrooms, thickly sliced
• 6 shallots, peeled and halved
• 1/2 cup garlic-herb cowboy butter, cut into pieces
• 1 oz dry au jus mix
• Creamy whipped mashed potatoes, for serving

Instructions

1. Place the sirloin steak tips in the bottom of a 6-quart slow cooker in an even layer. Scatter the sliced portobello mushrooms and the peeled shallots over the beef. No need to stir—just let the layers stay as they are.
2. Dot the garlic-herb cowboy butter over the top of the beef and vegetables. Sprinkle the dry au jus mix evenly over everything. Do not add any liquid—the butter and the meat's juices will create the gravy as they cook.
3. Cover the slow cooker and cook on LOW for 6 to 7 hours, or on HIGH for 3 to 4 hours, until the beef is fork-tender and the mushrooms are soft. Resist the urge to lift the lid during cooking—every peek lets out heat and adds time. Let it rest for 3 minutes before slicing.
4. After the minimum cooking time, check the beef. It should be fork-tender—a fork should slide in with almost no resistance. If it's still chewy, continue cooking for another 30 minutes and check again. The internal temperature should read at least 145°F (63°C) on an instant-read thermometer. Let it rest for 3 minutes before slicing.
5. Turn off the slow cooker and let the beef rest in the hot gravy for at least 3 minutes before serving. This allows the juices to redistribute through the meat, making each bite more succulent.
6. Spoon a generous portion of creamy whipped mashed potatoes onto each plate. Ladle the sirloin tips, mushrooms, shallots, and plenty of the garlic-butter au jus over the potatoes. Serve hot.

Contains: milk, gluten

Estimated nutrition per serving

Calories

420

Protein

38 g

Carbohydrates

12 g

Fat

24 g

Automatic estimate from the ingredient list, not laboratory-verified.