Portobello Steak Diane

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My partner and I do an at-home steak house night for Valentine’s Day every year. This tradition was born after a less-than-favorable experience at a very expensive steak house. The following year, we decided to take the steak house menu into our own hands and have never looked back. Steakhouse classics are, after all, fairly simple to make. And no matter how expensive a ribeye is in the grocery store, it’s guaranteed to be cheaper than any steak you’d order off a menu. Each year we tinker with these classics and come up with fun alternatives. These dishes maintain the spirit of the traditional chop house but are unique to us and our tastes. Today’s Portobello Steak Diane is our first plant-forward riff and I am head-over-heels in love with it.

Steak Diane is a classic steak dish that features a seared steak dressed in a cognac and cream pan sauce accented with tomato paste, mustard, and Worcestershire sauce. It resembles the French classic Steak au Poivre, but Steak Diane is not French. An Englishman named Tony Clerici claimed he invented it at his London restaurant Tony’s Grill in 1938. According to him, the dish was named in honor of Lady Diana Cooper. But enough about Steak Diane, let’s make Portobello Steak Diane!

We’re going to kick things off by making a marinade for our portobello mushrooms. Place olive oil, soy sauce, Dijon mustard, lemon juice, and a minced clove of garlic in a bowl. Add fresh ground pepper and whisk to combine. Place the mushrooms in a wide, shallow vessel or a freezer bag. Pour the marinade over the mushrooms and toss to coat. Transfer the mushrooms to the fridge and marinate for 30 minutes to an hour.

While the mushrooms are marinating, preheat the oven to 400°F. Once the mushrooms are good to go, heat some neutral oil in a large cast iron skillet. Add your mushrooms to the now-smoking skillet and sear them on both sides. This is more for appearance and for building up some extra fond to work with later.

Once the mushrooms are seared on both sides, transfer the skillet to the oven. Roast the mushrooms for 15 minutes before flipping them. Return the mushrooms to the oven and roast for 15 minutes more. The finished mushrooms should be quite tender. Transfer the mushrooms to a plate and keep them warm while you work on the pan sauce.

Now, the most important piece of advice I can give you for making this pan sauce is not to grab the skillet’s handle. I have done this so many times with so many different dishes and it sucks. Remember the pan was in a 400°F oven for 30 minutes. So this is not your typical stovetop preparation. I recommend placing a tea towel on the handle of the frying pan to remind you not to grab it willy-nilly. There is seriously nothing worse than a burn on the palm of your hand. 

Start by adding a couple of diced shallots to the pan. Keep the heat relatively low. The residual heat of the pan will be enough to soften and melt the shallots. Once the shallots are translucent, stir in some cognac to deglaze the pan. Simmer until the cognac is reduced by half. Pour in some veggie stock and add tomato paste, Dijon mustard, and Worcestershire sauce or soy sauce. I’m giving you an alternative because Worcestershire is technically not vegetarian. It contains anchovies. So if you are strictly vegetarian or vegan or you’re making this for somebody who is, use either a vegan Worcestershire sauce or failing that soy sauce. I know vegan Worcestershire can be difficult to track down.

Stir everything together and bring the mixture up to a spirited simmer. Once again, simmer until the sauce is reduced by half. You can tell your sauce has thickened when the bubbles on the surface of the sauce build and break at a slower and lazier pace. Pour in the cream and simmer for another 2-3 minutes or until thickened. Finish the sauce with a couple of pats of butter (dairy or plant-based) and stir until the butter has melted.

From here, it’s as simple as plating everything up. Place two portobello steaks on a plate and spoon the sauce over top. Finish with a sprinkling of finely chopped chives and serve immediately. I like to serve this dish with mashed potatoes, so make sure you save a little of that pan sauce for those. You can thank me later.

That’s everything you need to know about this Portobello Steak Diane. A plant-forward version of the 1930s British bistro classic.

Enjoy!