Equipment
Ingredients
Chunky Fries
- 500 g russet potatoes, peeled and cut into 1.5cm thick batons
- 30 ml olive oil
- 5 g kosher salt
Portobello Steaks
- 4 portobello mushrooms
- 15 ml olive oil
- 30 g unsalted butter
- 2 garlic, crushed
- 4 fresh thyme
Mustard Cream Sauce
- 1 shallot, finely minced
- 60 ml dry white wine
- 30 g dijon mustard
- 120 ml heavy cream, room temperature
- 60 ml vegetable stock, low sodium
- 5 g fresh chives, finely chopped
Nutrition (per serving)
Nutrition is estimated per serving. Nutrients without complete source data are omitted.
Full nutrition
- Calories
- 798 kcal
- Protein
- 12 g
- Carbohydrates
- 60 g
- Fat
- 58 g
- Fiber
- 7 g
- Sugar
- 9 g
- Sodium
- 1276 mg
- Saturated Fat
- 25 g
- Trans Fat
- 1 g
- Monounsaturated Fat
- 26 g
- Polyunsaturated Fat
- 5 g
- Cholesterol
- 100 mg
- Potassium
- 1873 mg
- Calcium
- 113 mg
- Iron
- 3.7 mg
- Magnesium
- 79 mg
- Phosphorus
- 403 mg
- Zinc
- 2.1 mg
- Vitamin A
- 369 mcg
- Vitamin C
- 20 mg
- Vitamin D
- 1.5 mcg
- Vitamin E
- 4.3 mg
- Vitamin K
- 22 mcg
- Vitamin B6
- 1.3 mg
- Vitamin B12
- 0.2 mcg
- Thiamin
- 0.36 mg
- Riboflavin
- 0.46 mg
- Niacin
- 10.7 mg
- Folate
- 94 mcg
- Water
- 449 g
- Alcohol
- 3 g
Sources: Aggregated Public Data, USDA FoodData Central
Method
Preheat the oven to 220C (430F). Position a rack in the center of the oven.
Place the potato batons into a mixing bowl. Toss thoroughly with 30ml of olive oil and the kosher salt until evenly coated.
Spread the potatoes in a single layer on a baking sheet, ensuring they do not overlap. Bake for 30 minutes, turning halfway through, until deeply golden and crispy on the edges.
While the fries bake, wipe the portobello mushroom caps gently with a clean kitchen towel to remove any dirt. Avoid rinsing them under running water.
Using a chef's knife, score the top of the mushroom caps lightly in a crosshatch pattern. This helps them absorb flavor and prevents curling.
Heat 15ml of olive oil in a large skillet over medium-high heat until shimmering. Add the mushrooms, cap-side down, and cook for 4 minutes per side.
Reduce the heat to medium. Add the butter, crushed garlic, and thyme sprigs to the skillet. Tilt the pan slightly and use a spoon to continuously baste the mushrooms with the foaming butter for 2 minutes.
Using tongs, remove the mushrooms from the skillet and set them aside on a plate to rest. Leave the flavorful fat in the pan.
In the same skillet over medium heat, add the minced shallot. Sauté for 1 minute until softened and translucent.
Pour the dry white wine into the skillet to deglaze, actively scraping the bottom of the pan to lift the browned mushroom and garlic bits.
Allow the wine to simmer and reduce by half, which should take about 2 minutes.
Lower the heat to medium-low. Whisk in the vegetable stock, Dijon mustard, and room-temperature heavy cream until the mixture is smooth and fully combined.
Simmer the sauce gently for 3 to 4 minutes until it thickens enough to lightly coat the back of a spoon. Taste and adjust seasoning with salt if necessary.
Return the resting portobello mushrooms and any accumulated juices on the plate back into the skillet. Spoon the sauce over the caps and warm through for 1 minute.
Divide the hot chunky fries and the mushroom steaks between warm plates. Drape the mushrooms generously with the remaining mustard cream sauce from the pan, and garnish with finely chopped chives.
Chef's Notes
- For the absolute best texture in your oven fries, soak the cut potatoes in cold water for 30 minutes to remove excess starch. Dry them completely with a towel before tossing with oil.
- Scoring the mushroom caps is a classic restaurant technique. It not only creates an attractive, steak-like presentation but also creates channels for the basting butter and mustard sauce to penetrate the mushroom.
- Do not substitute milk or half-and-half for the heavy cream. The lower fat content and higher water ratio in milk will cause the acidity of the wine and mustard to curdle the sauce.
- If your portobello mushrooms are particularly thick, you can place a smaller skillet on top of them during the first few minutes of searing to act as a press, ensuring an even crust.
Storage
Refrigerator: 3 days — Store sauce and mushrooms in an airtight container. Fries will become soggy and are best consumed immediately.
Reheating: Reheat mushrooms and sauce gently in a skillet over medium-low heat until warmed through. Crisp leftover fries in a 200C oven for 5 minutes.
Troubleshooting
Mushrooms release excessive water and boil instead of searing.
Cause: The pan was not hot enough initially, or the mushrooms were washed under running water instead of wiped.
Fix: Drain the excess liquid from the pan, increase the heat, and add a small splash of oil to re-initiate the searing process.
Prevention: Always dry-wipe mushrooms and wait until the pan oil is shimmering before adding them.
Mustard cream sauce looks grainy or split.
Cause: Cold cream was added to a boiling acidic reduction, or the heat was left too high during the simmering phase.
Fix: Remove from heat immediately and whisk vigorously. Adding a small splash of cold heavy cream can sometimes re-emulsify the sauce.
Prevention: Use room temperature cream and ensure the heat is lowered to medium-low before adding dairy.
Oven fries are soggy and pale.
Cause: Fries were overcrowded on the baking sheet, causing them to steam instead of roast.
Fix: Spread the fries out onto an additional pan and return to the oven, increasing the temperature to 230C (450F) for 5 minutes.
Prevention: Ensure there is adequate space between the potato batons; use two baking sheets if necessary.
Cultural Context
This dish is a vegetarian reimagining of the classic French bistro staple, Steak Frites. By substituting traditional cuts of beef with earthy, umami-rich portobello mushrooms and marrying them with a classic sauce moutarde, it delivers all the satisfying, rich, and tangy flavors of a Parisian brasserie without any meat.
