Slow-Cooker Portobello Herb Garlic Butter Pork Sirloin Roast Step-by-step instructions

Before you start

Before you start, make sure your slow cooker is clean and ready. Pat the pork sirloin roast dry with paper towels—this helps any seasonings adhere (though the recipe doesn't call for extra salt, the cowboy butter provides plenty of flavor). Slice the portobello mushroom caps into thick pieces, about 1/2-inch thick.

Mince the garlic if using fresh cloves; if using jarred minced garlic, measure out 2 tablespoons. If you're making your own cowboy butter, do that ahead and chill it so it can be sliced into neat medallions. Cook the egg noodles according to package directions just before serving, or keep them warm in a covered pot with a little butter.

Instructions

Layer and Season

1. 1Layer the Roast and Mushrooms
   Place the pork sirloin roast in the center of a 7-quart slow cooker. Scatter the thickly sliced portobello mushroom caps over and around the roast. Sprinkle the minced garlic evenly over the top.
   Look for The roast sits snugly in the cooker, mushrooms piled on top, garlic scattered over.
   Tip No need to sear the pork first—the slow cooker does all the work.
2. 2Top with Cowboy Butter
   Place the slices of garlic-herb compound cowboy butter evenly over the roast and mushrooms. The butter will melt as the cooker heats, basting the meat and creating a rich gravy.
   Look for Butter medallions sit on top, ready to melt into the meat.
   Tip If using homemade cowboy butter, keep it chilled until ready to slice so it holds its shape.

By the end of this phase, the pork roast sits in the center of the slow cooker, surrounded by thick slices of portobello mushrooms and a generous sprinkle of minced garlic. The cowboy butter medallions are placed on top, ready to melt. At this point, everything looks fresh and vibrant, with the earthy aroma of mushrooms and garlic mixing with the herb-scented butter. There's no cooking yet—just the promise of what's to come.

Slow Cook and Shred

3. 3Cook Low and Slow
   Cover the slow cooker and cook on LOW for 8 to 10 hours, until the pork is fork-tender and shreds easily. The internal temperature of the pork should reach at least 145°F (63°C), but for shredding, it will be well above that—around 190°F (88°C) for optimal tenderness. Let it rest for 3 minutes before slicing.
   Look for The meat is deeply browned, the mushrooms are soft, and the gravy is bubbling gently.
   Safe temperature 145°F (63°C) internal temperature (steaks, chops and roasts)
   Tip Avoid lifting the lid during cooking—each peek adds 20 minutes of cook time.
4. 4Shred the Pork
   Once the pork is fork-tender, transfer it to a cutting board. Let it rest for at least 5 minutes. Using two forks, shred the meat into bite-sized pieces, discarding any large fat pieces.
   Look for The pork pulls apart easily with little resistance.
   Tip Resting the meat before shredding keeps it moist and juicy.

After 8 to 10 hours on LOW, the kitchen fills with the rich, savory scent of slow-cooked pork and herbs. The meat is deeply browned and fork-tender, easily pulling apart. The mushrooms have softened and released their juices, and the butter has melted into a fragrant, glossy gravy.

The pork should shred with minimal effort, and the internal temperature should be well above 145°F (63°C). Check that the meat is fully tender and the gravy is bubbling gently.

Finish and Serve

5. 5Return Meat to Gravy
   Return the shredded pork to the slow cooker with the mushrooms and gravy. Stir gently to coat the meat in the buttery sauce. Let it warm through for about 10 minutes on LOW.
   Look for The shredded pork is glistening with gravy, and the sauce is thick and rich.
   Tip If the gravy seems thin, remove the lid and cook on HIGH for 15–20 minutes to reduce.
6. 6Serve Over Noodles
   Spoon the hot buttered egg noodles onto a serving platter or individual plates. Top generously with the shredded pork and mushrooms, and ladle extra gravy over the top.
   Look for Steaming piles of pork and noodles, with gravy pooling around the edges.
   Tip For a lower-carb option, serve over cauliflower mash or roasted vegetables.

The shredded pork is back in the slow cooker, coated in the buttery mushroom gravy. The noodles are warm and buttered, ready to receive the meat. The final dish is a generous pile of tender pork and mushrooms over noodles, with extra gravy ladled on top. The texture is silky and rich, and the aroma is irresistible. Give everything a final stir to ensure the meat is evenly coated, then serve immediately.

Common mistakes

The most common mistake is lifting the lid to check on the food—every time you do, heat escapes and the cooking time increases. Trust the process and keep the lid on. Another pitfall is using a roast that's too lean, like a tenderloin, which can dry out even in a slow cooker; stick with sirloin or shoulder.

Also, avoid overcrowding the cooker with too many mushrooms—they should be in a single layer over the meat. Finally, don't skip the resting time after cooking; letting the meat rest before shredding helps retain its juices.

How to tell it’s done

The pork is done when it is fork-tender and shreds easily with two forks. The internal temperature should register at least 145°F (63°C) for food safety, but for the best shredding texture, aim for 190°F (88°C) or higher—this ensures the collagen has fully broken down.

The mushrooms should be soft and deeply browned, and the gravy should be rich and slightly thickened, with a glossy sheen from the butter. If the gravy looks thin, remove the lid and cook on HIGH for 15–20 minutes to reduce and concentrate the flavors.

• Steaks, chops and roasts: 145°F (63°C) in the thickest part, then a 3-minute rest