If you’re craving a bold, steakhouse-style dinner at home, this Seared London Broil with Garlic Mashed Potatoes and Mushroom Pan Sauce delivers big flavor with a clean, intentional process. A deeply marinated London broil sears to perfection in a hot cast iron pan, then rests while you build a rich, umami-packed mushroom sauce in the same pan — using the reserved marinade to create layers of depth. Paired with creamy, garlicky Yukon gold mashed potatoes, this dish hits all the marks: texture, balance, and unapologetic flavor.
What Makes This Recipe Stand Out
Deep Flavor, Simple Flow – Marinate the steak overnight in a robust mix of soy sauce, balsamic, garlic, and herbs. Then sear it and let the pan do double-duty by transforming that same flavorful foundation into a luxurious sauce.
Pan Sauce That Works Smarter – Instead of discarding the marinade, it reduces with mushrooms, shallots, thyme, and cream — creating a restaurant-quality sauce that tastes slow-built but comes together quickly.
Garlic Mashed Potatoes That Actually Hit – Steaming Yukon golds prevents them from getting waterlogged, while mashed garlic butter and cream bring the richness. No lumps, no fuss — just smooth, flavorful comfort.
How to Make the Best Seared London Broil
- Marinate overnight – The acid and aromatics break down fibers in this lean cut while infusing it with flavor.
- Bring to room temp – Always let steak sit out 30 minutes before cooking to ensure an even sear.
- Sear first, in cast iron – High heat, minimal oil, and 4–5 minutes per side creates that caramelized crust and juicy center.
- Rest before slicing – Letting the steak sit for 10 minutes locks in moisture.
- Slice against the grain – Always. Thin slices make this lean cut tender and satisfying.
Creamy Garlic Mashed Potatoes, Done Right
Steamed Yukon gold potatoes mash perfectly with butter, cream, and garlic that’s been softened and blended into a paste. This technique delivers full garlic flavor without harshness, and a consistency that’s velvety without being heavy.Pro Tip: Mash the garlic with a pinch of salt to draw out its sweetness and help it melt seamlessly into the potatoes.
The Mushroom Sauce You’ll Want to Put on Everything
After your steak is seared and resting, the same pan transforms into the foundation for your sauce. Mushrooms sauté until golden, then the reserved marinade reduces with shallots, garlic, and fresh thyme. A splash of cream and a final swirl of butter create a sauce that’s earthy, silky, and packed with umami. Spoon it liberally over both the steak and mashed potatoes — it’s what brings everything together.
Why You’ll Keep Coming Back to This
- High flavor, low stress – Looks impressive, cooks easily.
- One pan, full payoff – Builds layers of flavor without multiple pots.
- Versatile and forgiving – Perfect for date night or weekly meal prep.
- Next-day flavor bomb – Leftovers taste even better tomorrow.
If you love steakhouse-style meals with a creative ingredient-driven twist, this is one to bookmark. It’s the kind of recipe that teaches you something valuable about timing and flow — how searing the steak first enhances the sauce, and how one thoughtful marinade can elevate an entire dish.
Serve it with a bold red wine, a crisp salad, and someone who truly appreciates a proper sear.
Seared London Broil with Mushroom Sauce and Garlic Mashed Potatoes
4
servings24
hours30
minutes24
hours30
minutesThis Seared London Broil with Garlic Mashed Potatoes and Mushroom Sauce is a steakhouse-quality meal made at home. A flavorful marinade, creamy garlic mashed potatoes, and a rich mushroom sauce made from the reduced marinade create the perfect balance of umami, tenderness, and indulgence.
Keeps the screen of your device on while you cook
Ingredients
- For the London Broil
1 London broil steak (~2 lbs)
1 cup water
1/2 cup soy sauce
1/2 cup extra virgin olive oil
3 cloves garlic, minced
1/4 cup red wine vinegar
1 tablespoon Worcestershire sauce
1 tablespoon dijon mustard
1 tablespoons honey
2-3 sprigs of thyme
2-3 sprigs of oregano
2-3 sprigs of parsley
1 tablespoon ground cumin
1 tablespoon paprika
1 teaspoon ground black pepper
1/2 teaspoon red pepper flakes
2 tablespoons avocado oil
- For the Mushroom Sauce
2 cups mushrooms (cremini or shiitake), sliced
1 tablespoon extra virgin olive oil
2 cloves garlic, minced
1 small shallot, minced
1 tablespoon thyme leaves, fresh
2 tablespoons unsalted butter
to tase, salt and ground black pepper
- For the Garlic Mashed Potatoes
1 pound Yukon gold potatoes
1/4 cup heavy cream
2 tablespoons butter
6 cloves of garlic, minced
to taste, salt and ground black pepper
Directions
- Marinate the London Broil:
In a blender, combine the water, soy sauce, extra virgin olive oil, red win vinegar, Worcestershire sauce, Dijon mustard, thyme, oregano, parsley, black pepper, and red pepper flakes.
Place the London broil in a resealable bag or shallow dish, and pour the marinade over it. Seal and marinate in the refrigerator for at least 4 hours, but preferably overnight. - Prepare the Garlic Mashed Potatoes:
Peel and chop the Yukon gold potatoes into evenly sized chunks. Place the potatoes in a steamer basket over simmering water and steam until fork-tender, about 20-25 minutes.
While the potatoes cook, melt the butter in a small saucepan over low heat. Add the minced garlic and cook until fragrant but not browned, about 1 minute. Drain the potatoes and return them to the pot. Add the garlic butter mixture and heavy cream. Mash until smooth and creamy, seasoning with salt and pepper to taste. Keep warm until ready to serve. - Sear the London Broil:
Remove the steak from the fridge 30 minutes before cooking to let it come to room temperature. Reserve 1 cup of the marinating the liquid for the sauce. Heat a cast iron skillet or grill pan over high heat. Oil the pan with avocado oil.
Pat the steak dry and sear for 4-5 minutes per side for medium-rare, or until desired doneness (130-135°F internal for medium-rare). Transfer to a cutting board and let rest for 10 minutes before slicing against the grain. - Cook the Mushroom Sauce:
Add the shallots and garlic, and cook until fragrant, 1-2 minutes. Stir in the sliced mushrooms and cook until they soften and begin to caramelize, 5-6 minutes. Pour in the reserved marinade and simmer until reduced by half, about 5-7 minutes. Stir in the butter and fresh thyme, and cook for another 2 minutes until slightly thickened. Season with salt and ground black pepper to taste. Keep warm until ready to serve. - Serve:
Plate the garlic mashed potatoes, then layer with slices of London broil. Spoon the mushroom sauce over the steak. Garnish with fresh thyme, cracked black pepper, or red pepper flakes, if desired.
Recipe Video
Notes
- Garlic Paste: To make the garlic more flavorful and less harsh, mince it finely and mash it into a paste with a little salt before adding it to the potatoes. This brings out its natural sweetness and blends seamlessly into the dish.
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