Cowboy Butter Portobello Tenderloin Tips: Slow-Cooker Dinner Step-by-step instructions

Before you start

Before starting, trim the beef tenderloin tips if needed and cut them into uniform 1-inch pieces so they cook evenly. Slice the portobello mushrooms thickly and peel the shallots, leaving them whole or halving them if they are large.

Have the garlic-herb cowboy butter softened so it is easy to dot over the ingredients. Measure out the dry au jus mix. No other prep is needed; the slow cooker does the rest.

Instructions

Layer the Ingredients

1. 1Prep and Layer the Ingredients
   Place the beef tenderloin tips in the bottom of a 6-quart slow cooker. Scatter the thickly sliced portobello mushrooms and the peeled, halved shallots over the beef. No need to stir; the layers will meld during cooking.
   Look for The slow cooker should be about half full with the beef, mushrooms, and shallots in even layers.
   Tip Pat the beef dry with paper towels before adding to the slow cooker for better browning, though browning is optional here.
2. 2Add the Butter and Au Jus
   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 meat juices will create a rich sauce as they cook.
   Look for The butter pieces and au jus powder should be visible on top of the beef and vegetables.
   Tip If the butter is very cold, cut it into small pieces so it distributes more easily.

At this point, the slow cooker contains raw beef, mushrooms, shallots, butter, and au jus mix. The ingredients should be layered in the order given, with the butter and au jus on top. The raw beef should be pink and the mushrooms firm. Everything should be dry and not mixed; the layers will combine as they cook. No heat is applied yet, so the aromas are just the fresh ingredients.

Slow-Cook Until Tender

3. 3Slow-Cook Until Tender
   Cover the slow cooker and cook on LOW for 6 to 8 hours, or on HIGH for 3 to 4 hours, until the beef is fork-tender and the mushrooms are soft. The sauce will be bubbling and fragrant. Let it rest for 3 minutes before slicing.
   Look for The beef should be easily pierced with a fork, and the sauce should be hot and bubbling around the edges.
   Safe temperature 145°F (63°C) internal temperature (steaks, chops and roasts)
   Tip Avoid lifting the lid during cooking, as this releases heat and extends the cooking time.

After several hours, the slow cooker will be bubbling gently, and the kitchen will smell richly beefy and buttery. The beef should be visibly tender, and the mushrooms will have darkened and softened.

The sauce will be a deep golden-brown, with the butter melted and combined with the meat juices. The shallots should be glossy and soft. Check that the beef is fork-tender before proceeding.

Rest and Serve

4. 4Rest and Serve
   Once the beef is tender, turn off the slow cooker and let the dish rest for at least 3 minutes before serving. The beef should reach an internal temperature of 145°F (63°C) if you check it. Serve the beef, mushrooms, and shallots with a generous ladle of the buttery au jus over mashed potatoes or crusty bread.
   Look for The sauce should be glossy and rich, and the beef should be tender but still moist.
   Safe temperature 145°F (63°C) internal temperature (steaks, chops and roasts)
   Tip Let the dish rest for at least 3 minutes so the juices redistribute; this keeps the beef tender.

Once the beef is tender, turn off the slow cooker and let the dish rest for at least 3 minutes. The sauce will settle slightly, and the beef will reabsorb some juices. When you lift a piece, it should be moist and tender. The mushrooms and shallots should be coated in the rich sauce. Serve immediately with mashed potatoes or crusty bread to soak up every last drop.

Common mistakes

One common mistake is adding extra liquid, thinking the dish will dry out. The beef and butter release plenty of juice, so no additional broth is needed. Another is lifting the lid frequently, which lets heat escape and lengthens cooking time.

Also, be careful not to overcook the beef on high, as it can become dry; low and slow is best. Finally, make sure the mushrooms are sliced thick enough—thin slices may disintegrate during the long cooking time.

How to tell it’s done

The dish is done when the beef is fork-tender and easily pulls apart, and the mushrooms are soft and have absorbed the sauce. If you check the internal temperature, the beef should read 145°F (63°C) for medium-rare, but because it’s cooked low and slow, it will be more tender than a quick-cooked steak.

The sauce should be bubbling and slightly thickened, and the shallots should be translucent and sweet. Let the dish rest for at least 3 minutes before serving to allow the juices to redistribute.

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