Equipment
Ingredients
Baked Potatoes
- 4 baking potatoes, whole, scrubbed
- 15 ml olive oil, for rubbing
- 5 g sea salt, coarse
Leek Filling
- 2 leeks, white and light green parts only, sliced into half-moons
- 30 g unsalted butter
- 2 garlic, minced
- 2 g fresh thyme leaves
Cheese Sauce (Mornay)
- 30 g unsalted butter
- 30 g all-purpose flour
- 400 ml whole milk, warm
- 150 g sharp cheddar cheese, freshly grated
- 5 g dijon mustard
- 1 g nutmeg, freshly grated
- 1 g cayenne pepper
Nutrition (per serving)
Nutrition is estimated per serving. Nutrients without complete source data are omitted.
Full nutrition
- Calories
- 637 kcal
- Protein
- 20 g
- Carbohydrates
- 69 g
- Fat
- 32 g
- Fiber
- 9 g
- Sugar
- 11 g
- Sodium
- 844 mg
- Saturated Fat
- 18 g
- Monounsaturated Fat
- 7 g
- Polyunsaturated Fat
- 1 g
- Cholesterol
- 42 mg
- Potassium
- 1542 mg
- Calcium
- 459 mg
- Iron
- 3.5 mg
- Magnesium
- 107 mg
- Phosphorus
- 491 mg
- Zinc
- 2.8 mg
- Vitamin A
- 348 mcg
- Vitamin C
- 37 mg
- Vitamin D
- 1.3 mcg
- Vitamin E
- 1.1 mg
- Vitamin K
- 9 mcg
- Vitamin B6
- 0.7 mg
- Vitamin B12
- 0.5 mcg
- Thiamin
- 0.27 mg
- Riboflavin
- 0.28 mg
- Niacin
- 3.5 mg
- Folate
- 62 mcg
- Water
- 337 g
Sources: Aggregated Public Data, USDA FoodData Central
Method
Preheat oven to 200°C (400°F). Poke holes in the potatoes with a fork, rub with olive oil, and coat generously with sea salt. Place directly on the oven rack (with a tray below to catch drips) and bake for 60-75 minutes until the skin is crisp and the inside yields to pressure.
While potatoes bake, thoroughly wash the sliced leeks in a bowl of cold water to remove grit. Lift them out (leaving grit at the bottom) and pat dry.
In a sauté pan over medium heat, melt 30g butter. Add the leeks and a pinch of salt. Sweat gently until completely soft and sweet, but not browned. Stir in garlic and thyme for the last minute.
For the sauce: In a saucepan over medium heat, melt 30g butter. Whisk in the flour and cook for 1-2 minutes to cook out the raw taste (blond roux).
Gradually whisk in the warm milk to avoid lumps. Simmer gently for 5 minutes until thickened enough to coat the back of a spoon.
Remove sauce from heat. Stir in mustard, nutmeg, cayenne, and 100g of the cheddar cheese until smooth. Reserve the remaining 50g cheese for topping.
When potatoes are done, cut them in half lengthwise. Carefully scoop out the flesh into a bowl, leaving a 5mm (1/4 inch) layer of potato attached to the skin to maintain structural integrity.
Mash the scooped potato flesh roughly. Fold in the sautéed leeks and half of the cheese sauce. Taste and adjust salt and pepper.
Spoon the mixture back into the potato skins. Pour the remaining cheese sauce over the top and sprinkle with the reserved cheddar.
Return to the oven (or switch to broiler/grill) for 10-15 minutes until the cheese is bubbling and golden brown spots appear.
Chef's Notes
- Always wash leeks after slicing. Dirt gets trapped deep between the layers that you can't reach when the leek is whole.
- For the fluffiest texture, mash the potato flesh while it is still steaming hot. If it cools down, it becomes gummy.
- Grate your own cheese. Pre-shredded bags contain anti-caking agents (cellulose) that prevent the sauce from melting smoothly.
- Rubbing the potato skins with oil and salt before the initial bake ensures the skin is tasty and crisp—often the best part of the dish.
Storage
Refrigerator: 3 days — Store in an airtight container. Sauce may thicken significantly.
Reheating: Reheat in a 180°C (350°F) oven for 20-25 minutes. Microwaving is possible but will soften the skin.
Troubleshooting
Cheese sauce is grainy or oily
Cause: The sauce was boiled after adding the cheese, causing the proteins to curdle and fat to separate.
Fix: Let it cool slightly and blend with an immersion blender to re-emulsify.
Prevention: Remove the white sauce from the heat completely before stirring in the cheese.
Potato skins collapse
Cause: Scooped out too much flesh or potato was overcooked.
Fix: Place the skins in a muffin tin or ramekins to hold their shape while baking.
Prevention: Leave a generous wall of potato inside the skin when scooping.
Cultural Context
The 'Jacket Potato' is a British institution, serving as everything from a cheap lunch to a comforting dinner. While typically topped simply with beans or tuna, this version elevates the humble spud with a technique similar to 'Potatoes Romanoff' or a Twice-Baked Potato, incorporating French sauce techniques.