Slow Cooker Pork Sirloin Roast with Mushroom Garlic Butter Step-by-step instructions

Before you start

Before you start, make sure your slow cooker is clean and ready. If you're using a frozen pork roast, thaw it in the refrigerator overnight — do not put a frozen roast directly into the slow cooker, as it may not cook evenly and could pose a food safety risk. Have your ingredients measured and ready: the onion soup mix, the halved mushrooms, and the butter medallions.

If you're making your own garlic-herb butter, do that ahead of time so it's firm enough to slice. Set out a cutting board and a couple of forks for shredding later. Also, consider cooking your egg noodles or other side dish just before serving so they're warm and ready.

Instructions

Build the Pot

1. 1Place the Roast
   Place the pork sirloin roast in the center of the slow cooker. It can be straight from the fridge; no need to bring it to room temperature first. If the roast is tied, leave the twine on for even cooking — it will be easy to remove after.
   Look for The roast sits snugly in the bottom of the slow cooker, leaving a little space around the edges.
   Tip For even cooking, tuck any thin ends under so the roast is relatively uniform in thickness.
2. 2Season with Onion Soup Mix
   Sprinkle the dry onion soup mix evenly over the entire surface of the roast. Use your fingers or the back of a spoon to pat it gently so it sticks to the meat; this creates a savory crust as it cooks.
   Look for The roast is evenly coated with a light brown seasoning layer.
   Tip Don't skip patting the mix down — it helps the seasoning stay on the meat instead of washing off into the liquid.
3. 3Add the Mushrooms
   Scatter the halved cremini mushrooms around the sides of the roast, tucking them into the gaps. They will braise in the meat juices and butter, becoming tender and flavorful.
   Look for Mushrooms fill the spaces around the roast, nestled against the meat.
   Tip Use small cremini mushrooms or quarter larger ones so they cook evenly and can be scooped up with the pork.
4. 4Top with Garlic-Herb Butter
   Place the medallions of garlic-herb compound butter evenly across the top of the roast. As the slow cooker heats, the butter will melt and seep down over the meat and mushrooms, creating a rich, aromatic gravy.
   Look for Butter medallions sit on top of the roast, ready to melt.
   Tip If the butter is too hard to slice, let it sit at room temperature for a few minutes before cutting.

At the end of this phase, the slow cooker contains the raw pork roast seasoned with onion soup mix, surrounded by halved cremini mushrooms, and topped with medallions of garlic-herb butter. The ingredients are arranged so the butter will melt and flavor the meat and mushrooms as it cooks. The roast should be centered, and the mushrooms should be tucked around the sides, not piled on top. The butter should be placed on the highest point of the roast so it melts down over the surface.

Slow Cook to Tender

5. 5Slow Cook Until Fork-Tender
   Cover the slow cooker and cook on LOW for 8 to 10 hours, or on HIGH for 4 to 5 hours, until the pork is fork-tender and shreds easily. The internal temperature should reach at least 145°F (63°C) for food safety, but for shredding it will be higher, around 190-200°F (88-93°C). Let it rest for 3 minutes before slicing.
   Look for The meat is so tender that a fork slides in with no resistance, and it begins to pull apart.
   Safe temperature 145°F (63°C) internal temperature (steaks, chops and roasts)
   Tip Cooking on LOW is preferred for the most tender results. If short on time, HIGH works, but the meat may be slightly less shreddable.
6. 6Shred the Pork
   Once the pork is fork-tender, remove it to a cutting board and let it rest for at least 3 minutes. Then, using two forks, shred the meat into bite-sized pieces, discarding any large fat chunks or twine. Return the shredded pork to the slow cooker and stir gently to coat with the gravy.
   Look for The pork pulls apart easily into moist, tender strands.
   Safe temperature 145°F (63°C) internal temperature (steaks, chops and roasts)
   Tip Letting the meat rest before shredding helps it retain its juices, making the final dish more succulent.

After the cooking time, the slow cooker should be filled with a rich, fragrant liquid — a mix of melted butter, pork juices, and seasonings. The meat should be fork-tender, easily pulling apart with little resistance.

The mushrooms will have softened and absorbed the sauce, turning a deeper brown. The aroma is savory and garlicky, with a hint of herbs. The liquid should be bubbling gently around the edges. If the meat is still firm, cover and continue cooking, checking every 30 minutes.

Shred and Serve

7. 7Serve with Buttered Noodles
   Serve the shredded pork and mushrooms over warm buttered egg noodles, spooning extra gravy over the top. The rich, garlicky sauce is the star — don't skimp on it.
   Look for Steaming mounds of pork and mushrooms sit atop a bed of glossy noodles, bathed in buttery gravy.
   Tip For a low-carb option, serve over mashed cauliflower or alongside steamed green beans.

The shredded pork is returned to the slow cooker and coated with the buttery gravy. The mushrooms are nestled among the meat, and the sauce is thick enough to cling to the strands. When served over buttered noodles, the dish looks hearty and comforting, with the pork glistening and the mushrooms adding an earthy touch. The final dish should be steaming hot, with a rich, savory aroma that invites you to dig in.

Common mistakes

One common mistake is lifting the lid too often to check on the roast. Every time you lift the lid, heat escapes and the cooking time extends. Trust the process and resist the urge to peek until the minimum cooking time has passed.

Another mistake is using a pork loin instead of a sirloin roast — pork loin is leaner and can dry out even in a slow cooker. Stick with sirloin or shoulder. Finally, don't skip the resting step before shredding; it allows the juices to redistribute, making the meat more moist and flavorful.

How to tell it’s done

The pork is done when it is fork-tender — you can easily insert a fork into the thickest part and twist it without resistance. For food safety, the internal temperature should reach at least 145°F (63°C), but for shredding, it will typically be much higher, around 190-200°F (88-93°C).

The meat should pull apart easily into strands, and the mushrooms should be soft and infused with the buttery sauce. If the pork is still tough, it needs more time. Continue cooking and check every 30 minutes until it reaches the desired tenderness.

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