Equipment
* optional
Ingredients
Chunky Fries
- 800 g russet potatoes, cut into thick batons
- 30 ml olive oil
- 5 g sea salt
Portobello Steaks
- 400 g portobello mushrooms, stems removed, wiped clean
- 30 ml olive oil
- 15 ml balsamic vinegar
- 2 garlic, minced
- 2 fresh thyme, leaves picked and roughly chopped
Dijon Cream Sauce
- 15 g unsalted butter
- 1 shallot, finely diced
- 60 ml dry white wine
- 150 ml heavy cream, room temperature
- 30 g dijon mustard
- 15 g whole grain mustard
- sea salt
- black pepper
- 5 g fresh parsley, finely chopped
Nutrition (per serving)
Nutrition is estimated per serving. Nutrients without complete source data are omitted.
Full nutrition
- Calories
- 502 kcal
- Protein
- 8 g
- Carbohydrates
- 46 g
- Fat
- 33 g
- Fiber
- 5 g
- Sugar
- 6 g
- Sodium
- 837 mg
- Saturated Fat
- 13 g
- Trans Fat
- 0 g
- Monounsaturated Fat
- 16 g
- Polyunsaturated Fat
- 3 g
- Cholesterol
- 50 mg
- Potassium
- 1322 mg
- Calcium
- 77 mg
- Iron
- 2.8 mg
- Magnesium
- 60 mg
- Phosphorus
- 267 mg
- Zinc
- 1.4 mg
- Vitamin A
- 187 mcg
- Vitamin C
- 16 mg
- Vitamin D
- 0.9 mcg
- Vitamin E
- 2.7 mg
- Vitamin K
- 35 mcg
- Vitamin B6
- 0.9 mg
- Vitamin B12
- 0.1 mcg
- Thiamin
- 0.26 mg
- Riboflavin
- 0.28 mg
- Niacin
- 6.7 mg
- Folate
- 64 mcg
- Water
- 308 g
- Alcohol
- 2 g
Sources: USDA FoodData Central
Method
Preheat your oven to 220C (430F). Toss the potato batons thoroughly with olive oil and sea salt. Spread them evenly in a single layer on a large baking sheet. Roast for 40 to 45 minutes, turning them halfway through, until they are golden brown and crispy on the outside.
While the fries are baking, prepare the marinade for the mushrooms. In a small mixing bowl, whisk together the olive oil, balsamic vinegar, minced garlic, and fresh thyme. Use a pastry brush or a spoon to coat both sides of the portobello caps evenly with the mixture.
Heat a large skillet over medium-high heat. Place the marinated portobello mushrooms in the pan, smooth side down. Sear for 4 to 5 minutes per side until deeply caramelized and tender. Remove the mushrooms from the skillet and set them aside on a warm plate.
Lower the heat under the skillet to medium and add the unsalted butter. Once melted, add the finely diced shallot. Cook for 2 to 3 minutes, stirring constantly, until the shallot is softened and translucent. Scrape up any browned bits left from the mushrooms.
Pour the dry white wine into the skillet to deglaze the pan. Let the liquid bubble gently and reduce by half, which should take about 2 minutes.
Reduce the heat to medium-low. Whisk the heavy cream, Dijon mustard, and whole grain mustard into the reduced wine. Simmer gently for 3 to 4 minutes until the sauce thickens enough to coat the back of a spoon. Taste and adjust the seasoning with sea salt and freshly ground black pepper.
Arrange the warm portobello steaks alongside the crispy chunky fries on individual plates. Spoon the hot mustard cream sauce generously over the mushrooms and sprinkle with chopped fresh parsley. Serve immediately.
Chef's Notes
- For the crispiest oven fries, soak the cut potatoes in cold water for 30 minutes to wash away excess surface starch. Drain and dry them completely with a clean kitchen towel before tossing with oil, as surface moisture prevents crisping.
- Do not wash portobello mushrooms under running water. They act like sponges and will absorb the water, releasing it into the pan and preventing a proper sear. Simply wipe them clean with a slightly damp paper towel.
- Heavy cream is mandatory for this sauce. Its high fat content acts as a stabilizer, preventing the dairy from curdling when it hits the acidic white wine and mustard. Lower-fat alternatives like milk or half-and-half will almost certainly split.
- Lightly scoring the smooth tops of the portobello mushrooms in a shallow crosshatch pattern before marinating allows the balsamic and garlic flavors to penetrate much deeper into the dense flesh.
Storage
Refrigerator: 3 days — Store sauce, mushrooms, and fries in separate airtight containers.
Reheating: Reheat fries in a 200C oven for 10 minutes until crisp. Warm the mushrooms and sauce together gently in a skillet over low heat, adding a splash of water if the sauce has thickened too much.
Troubleshooting
Sauce separates, looks greasy or curdled
Cause: Boiling the cream vigorously or adding the acidic mustard while the heat was too high
Fix: Remove the pan from the heat immediately and vigorously whisk in a splash of cold heavy cream or water to bring the emulsion back together
Prevention: Always lower the pan heat significantly before whisking in the cream and mustard
Fries are pale, soft, and completely lacking crispness
Cause: Overcrowding the baking sheet, which trapped moisture and caused the potatoes to steam instead of roast
Fix: Cannot be fixed
Prevention: Ensure potatoes are arranged in a single layer with empty space between each piece, using two baking sheets if necessary
Cultural Context
Steak Frites is a cornerstone of French brasserie dining, traditionally featuring a pan-seared beef steak paired with deep-fried potatoes. This modern adaptation celebrates the robust, umami-rich qualities of portobello mushrooms, offering a plant-based alternative that retains the luxurious, comforting essence of the original dish through its classic Dijon cream sauce.
