Keto Philly Cheesesteak Portobello Mushrooms

Why You’ll Love This Recipe

• All the classic Philly cheesesteak flavors without the bread, keeping carbs low.
• Weeknight-friendly: 35 minutes, one skillet, and a quick broil to finish.
• Portobellos stay meaty and juicy while the provolone melts into a bubbly blanket.
• Easy to customize with your favorite peppers, spice level, and cheese.

Grocery List

• Produce: Portobello caps, green bell pepper, red bell pepper, yellow onion, garlic, parsley
• Dairy: Provolone cheese, unsalted butter
• Pantry: Shaved ribeye or thin-sliced beef, avocado/olive oil, Worcestershire sauce, kosher salt, black pepper, foil

Full Ingredients

For the mushroom caps

• 4 large portobello mushroom caps (4–5 inches wide), stems trimmed, gills scraped if heavy
• 1 tbsp avocado or olive oil
• 1/2 tsp kosher salt
• 1/4 tsp freshly ground black pepper

For the cheesesteak filling

• 1 lb shaved ribeye or thinly sliced beef (sirloin or top round also work)
• 1 tbsp avocado or olive oil
• 1 tbsp unsalted butter
• 1 medium green bell pepper, thinly sliced (about 1 cup)
• 1 small red bell pepper, thinly sliced (about 1 cup)
• 1 small yellow onion, thinly sliced (about 1 cup)
• 2 garlic cloves, minced
• 1 tsp Worcestershire sauce
• 1 tbsp beef broth or water (optional, for deglazing)
• 1/2 tsp kosher salt
• 1/4 tsp freshly ground black pepper

For topping and garnish

• 8 thin slices provolone cheese (about 6 oz), 2 slices per cap
• 1 tbsp chopped fresh parsley (optional)

Step-by-Step Instructions

Step 1: Preheat and set up the pan

Set your oven to broil on High and position a rack 6 inches below the heating element. Line a rimmed sheet pan with foil for easy cleanup and set a wire rack on top to keep the mushrooms elevated so they broil instead of steam.

Step 2: Prep the portobellos

Wipe the mushroom caps clean with a damp paper towel. Twist off the stems and gently scrape out the dark gills if they are thick; this reduces moisture and keeps the filling from turning black. Brush the caps all over with 1 tablespoon oil and season with 1/2 teaspoon salt and 1/4 teaspoon pepper.

Step 3: Broil the caps

Arrange mushrooms gill-side up on the rack. Broil for 4 minutes, flip, and broil 2–3 minutes more until just tender. Remove, carefully pour off or blot any liquid pooled in the caps, and set aside while you make the filling.

Step 4: Sauté peppers and onions

Heat a large skillet over medium-high. Add the remaining 1 tablespoon oil and the butter. Once shimmering, add the green pepper, red pepper, and onion with a pinch of salt. Cook, stirring occasionally, until tender with browned edges, 6–8 minutes. Stir in the minced garlic for 30 seconds until fragrant. If the pan is dry, splash in 1 tablespoon beef broth or water and scrape up any browned bits. Transfer veggies to a bowl.

Step 5: Sear the shaved beef

Increase the heat to high. Add the shaved beef in an even layer, seasoning with 1/2 teaspoon salt, 1/4 teaspoon pepper, and the Worcestershire. Sear, tossing just once or twice, 2–3 minutes total until the beef is just cooked through and still juicy. Return the peppers and onions to the skillet and toss to combine. Taste and adjust seasoning.

Step 6: Stuff and broil with provolone

Mound the cheesesteak mixture into the broiled mushroom caps, packing it down slightly. Top each cap with 2 slices of provolone, letting the edges drape over the sides. Broil on High for 2–3 minutes, watching closely, until the cheese is fully melted with light golden spots.

Step 7: Rest, garnish, and serve

Let the stuffed caps rest for 2 minutes so the juices settle. Sprinkle with chopped parsley and serve hot. Spoon any pan juices over the top for extra flavor.

Pro Tips

• Use a wire rack on your sheet pan so the mushrooms don’t sit in their juices and go soggy.
• Scraping heavy gills and blotting after the first broil pass keeps the filling bright and the caps meaty, not watery.
• Cook shaved beef fast and hot. Overcooking makes it tough; aim for just-browned edges.
• Slice peppers and onions thinly so they soften quickly but still have a little bite after broiling.
• If your broiler runs hot, crack the oven door and check every 30 seconds during the final melt.

Variations

• Chicken Philly: Swap beef for thinly sliced chicken thighs; cook 4–5 minutes until just done.
• Spicy: Add sliced jalapeño with the peppers and finish with red pepper flakes.
• Creamy provolone sauce: Whisk 2 oz cream cheese with 2 tbsp heavy cream over low heat; stir in 2 oz shredded provolone and a pinch of garlic powder, then spoon over the stuffed caps instead of sliced cheese.

Storage & Make-Ahead

Refrigerate leftovers in an airtight container for up to 3 days. Reheat on a foil-lined sheet at 375°F for 10–12 minutes until hot and the cheese re-melts, or broil 1–2 minutes if you want more browning. Make-ahead: Broil the mushroom caps and cook the cheesesteak filling up to 2 days in advance. Store separately; stuff, top with cheese, and broil just before serving. The filling also freezes well for up to 2 months; thaw overnight in the fridge.

Nutrition (per serving)

Approximate per stuffed cap: 600 calories; 45 g fat; 30 g protein; 9 g total carbs; 3 g fiber; 6 g net carbs. Nutrition will vary based on exact beef cut and cheese thickness.