Slow-Cooker Guinness Onion Dijon Pork Sirloin Roast

This slow-cooker pork sirloin roast is the ultimate set-it-and-forget-it dinner. With just five ingredients and five minutes of prep, you can have a rich, savory meal that tastes like it simmered all day—because it did.

The combination of Guinness, pearl onions, sour cream, and Dijon creates a deeply flavorful gravy that coats every shred of tender pork. Serve it over rice for a complete, satisfying dinner that will become a weeknight favorite.

Pork sirloin roast is an underrated cut that becomes incredibly tender when cooked low and slow. Here, it's braised in a mixture of Guinness stout, au jus, and aromatics, then finished with a swirl of sour cream and whole-grain mustard.

The result is a fork-tender pork with a velvety, tangy gravy that's perfect for spooning over rice or mashed potatoes. This recipe is all about minimal effort and maximum flavor—just dump everything into the slow cooker and let time do the work.

Ingredients

Why this recipe works

Cooking the pork sirloin roast on LOW for 8 hours allows the connective tissue to break down, turning a lean cut into melt-in-your-mouth shreds. The slow, moist heat ensures the meat stays juicy and never dries out. The Guinness adds depth and a slight bitterness that balances the richness of the sour cream and Dijon, creating a complex sauce that clings to every bite.

The method is intentionally hands-off. Layering the ingredients without stirring means the sour cream and mustard melt into the sauce as the pork cooks, creating a creamy, cohesive gravy. The pearl onions soften and sweeten, absorbing the stout and meat juices. This one-pot approach not only saves time but also allows the flavors to meld and develop over hours of gentle simmering.

Notes and substitutions

Pork sirloin roast is a lean, boneless cut that benefits from long, slow cooking. If unavailable, a pork shoulder or butt can be used, though it will be richer and may require slightly longer cooking.

Pearl onions are small and sweet; if using frozen, there's no need to thaw them first. Whole-grain Dijon mustard provides texture and a robust mustard flavor—smooth Dijon can be substituted, but reduce the amount slightly to avoid overpowering the dish.

A 6-quart slow cooker is ideal for this recipe. If using a smaller cooker, cut the roast to fit. The au jus can be store-bought or homemade; beef broth is a fine substitute.

For a thicker sauce, remove the pork and onions and simmer the sauce on the stovetop for a few minutes, or whisk in a cornstarch slurry. This recipe is naturally gluten-free if using gluten-free au jus and mustard, but always check labels.

• Guinness stout: Use any dark stout or porter; for a non-alcoholic version, use beef broth with a splash of balsamic vinegar.
• Pearl onions: Substitute with 1 cup frozen pearl onions, thawed, or use a small yellow onion cut into wedges.
• Au jus: Use beef broth or a combination of beef broth and a splash of Worcestershire sauce.
• Sour cream: Replace with plain Greek yogurt or crème fraîche for a similar tangy creaminess.

Equipment

• 6-quart slow cooker
• Measuring cups and spoons
• Cutting board
• Chef's knife
• Serving spoon
• Tongs
• Plate for serving