Leek Gratin
A creamy, plant-based leek gratin baked with a miso-mustard béchamel and topped with crunchy hazelnuts and breadcrumbs. A nutritious, flavorful side dish that’s high in fiber, rich in plant protein, and perfect for everyday cooking or meal prep.
Equipment
- 1 ovenproof casserole dish (about 26 cm / 10 in)
- 1 Medium saucepan
- 1 Whisk
- 1 Mixing Bowl
- flexible
- 1 Kitchen Knife
- 1 Chopping Board
Ingredients
For the Leeks & Béchamel
- 60 ml ¼ cup olive oil, divided
- 800 g 28 oz, approx. 4 leeks, trimmed
- 25 g 3 tbsp all-purpose flour (or chickpea flour for GF)
- 500 ml 2 cups unsweetened plant milk (almond, oat, or soy)
- 10 g 2 tsp white miso paste
- 1 tbsp wholegrain mustard adjust to taste
- 4 tbsp nutritional yeast
- 2 tsp fresh thyme leaves or chopped rosemary
- 1 squeeze of fresh lemon juice optional, zest reserved for topping
- Salt and black pepper to taste
- Freshly grated nutmeg to taste
For the Topping (Optional)
- 65 g ½ cup hazelnuts, chopped
- 25 g ½ cup coarse breadcrumbs (GF if needed)
- Zest of ½ lemon
- Pinch of salt and pepper
- 25 g 2 tbsp vegan butter (or olive oil)
Instructions
- Prepare the Leeks: Begin by trimming away the tough dark-green tops of the leeks, reserving them if you’d like to make homemade stock later. Remove any wilted or dirty outer layers, then rinse the leeks thoroughly under running water to remove hidden grit between the layers. Pat them dry with a clean kitchen towel. Slice the cleaned leeks into thick rounds, about 2.5 cm (1 inch) in size, so they hold their shape during baking.
- Char the Leeks for Depth of Flavor: Place your ovenproof casserole dish (about 26 cm / 10 in) on the stovetop over medium heat. Add 1 tablespoon of olive oil and let it warm. Arrange the leek pieces cut-side down in a single layer. Allow them to cook undisturbed for a few minutes until lightly golden and caramelized. Gently flip to sear the other side. This step enhances the natural sweetness of leeks and gives the gratin a deeper, more savory flavor. Once both sides are charred, transfer the leeks to a plate.If the bottom of the dish has a heavy burnt layer, wipe it clean before baking; if it’s only lightly browned, leave it for extra flavor.
- Preheat the Oven: Set your oven to 200°C (390°F) so it’s ready when the gratin goes in. A hot oven ensures the béchamel thickens and the topping turns golden and crisp.
- Make the Flavor Base for Béchamel: In a small bowl, whisk the miso paste with a splash of the plant milk to dissolve it into a smooth liquid. This prevents clumps and ensures the umami flavor blends evenly into the sauce later.
- Cook the Roux: In a medium saucepan, heat the remaining olive oil over low heat. Sprinkle in the flour and immediately whisk until it forms a loose paste (called a roux). Cook the roux for about 1 minute, stirring constantly, just until the raw flour taste cooks off. Be careful not to let it brown—the goal here is a pale, smooth base for your sauce.
- Build the Béchamel Sauce: Gradually pour in the plant milk while whisking constantly to avoid lumps. Once all the milk is incorporated, whisk in the diluted miso, mustard, and nutritional yeast. Continue stirring as the mixture gently simmers and thickens into a silky sauce. Season with salt, black pepper, a good grating of nutmeg, and the fresh thyme leaves. If you enjoy a touch of brightness, squeeze in a little lemon juice. Taste and adjust seasoning as needed—this sauce is the backbone of your gratin, so make it flavorful.
- Prepare the Crunchy Topping: In a mixing bowl, combine the chopped hazelnuts, breadcrumbs, lemon zest, salt, and pepper. Add the softened vegan butter (or olive oil) and use your fingers or a flexible spatula to rub it into the mixture until everything is evenly coated. The butter helps the topping crisp up beautifully in the oven.
- Assemble the Gratin: Return the charred leeks to the ovenproof dish, spreading them into an even layer. Pour the warm béchamel sauce over the leeks—just enough to cover them. The sauce should seep between the layers, coating the leeks without drowning them.
- Bake Covered for Tenderness: Cover the dish with its lid (or tightly with aluminum foil if using a dish without a lid). Place in the preheated oven and bake for 15 minutes. Covering the gratin at this stage allows the leeks to steam gently in the sauce, becoming tender without drying out.
- Uncover and Continue Baking: After 15 minutes, remove the lid or foil and return the dish to the oven. Bake uncovered for another 10–15 minutes, until the sauce thickens slightly and begins to bubble around the edges. This step concentrates the flavors and gives the béchamel a luxurious texture.
- Add the Crunchy Topping: Sprinkle the prepared hazelnut and breadcrumb mixture evenly over the top of the bubbling gratin. Return the dish to the oven for an additional 5–10 minutes, or until the topping is golden-brown and crisp. Keep a close eye to avoid burning—every oven browns a little differently.
- Serve and Enjoy: Remove the gratin from the oven and let it sit for a few minutes to settle before serving. The sauce will thicken slightly as it cools, making it easier to portion. Serve warm as a flavorful side dish or enjoy it as a light main with crusty sourdough bread or a simple green salad.
Notes
- Use only the tender white and light-green parts of leeks for the best texture; dark green tops can be reserved for stock.
- To make the gratin gluten-free, substitute all-purpose flour with chickpea flour and use gluten-free breadcrumbs.
- Nutritional yeast provides a cheesy flavor in vegan versions; for a more indulgent taste, add vegan hard cheese.
- Adjust seasoning after making the béchamel, keeping in mind that leeks absorb flavors during baking.
- For a heartier dish, stir in a can of drained cannellini beans, cubed leftover potatoes, or cooked wholemeal pasta.
- The hazelnut topping can be replaced with walnuts or almonds for a slightly different crunch.
- Lemon zest brightens the dish—add it to the topping for a fresh, aromatic note.
