Ingredients
Method
- Preheat the oven to 350°F/175°C and grease a large oval or rectangular (9x13 inch) baking dish with butter.
- Wash the leeks thoroughly, getting water between the layers, then slice into 1-1 ¼ inch rounds, using only the light green and white parts. If the leeks still look dirty, wash again, moving around the layers to loosen any stuck dirt. Thoroughly pat the leeks dry (this is important so they sear instead of steam). Season the leek rounds with salt.
- In a large skillet over medium-high, heat the oil. Add in the leeks in a single layer, searing for 4-5 minutes until golden brown, then flip and sear another ~3 minutes. If needed, work in batches and add more oil.
- Arrange the seared leeks in a single layer in the prepared baking dish.
- Gently crush the peppercorns. You can do this with a mortar and pestle, or place the peppercorns in a plastic bag and smash with a rolling pin.
- Using the same pan that you cooked the leeks in, reduce heat to medium and add in the butter, shallots and cracked peppercorns. Cook for 1-2 minutes, until the shallot starts to soften and the pepper is fragrant.
- Turn off the heat, then add in the cognac, return to heat and continue cooking until most of the cognac has cooked off. Add in the stock and simmer until it's reduced by half.
- Lower the heat and stir in the heavy cream, thyme, Dijon, Worcestershire and salt. Simmer for 2-3 minutes, until it coats the back of a spoon.
- Pour the sauce evenly over the leeks. Cover with foil, then bake for 25-35 minutes, until a knife easily pierces the darker green medallions.
- In a bowl, toss together the breadcrumbs and both cheeses. After 25-35 minutes, turn the oven to broil. Top the leeks with the breadcrumb mixture and return to the oven to broil for about 4 minutes, watching closely, until golden brown and bubbling.
- Garnish with chives and serve warm!
Notes
Clean the leeks thoroughly! Rinse each round under cold water, separating the layers, and rinse again if you see any grit.
Peppercorns: crack coarsely, not finely. A mortar and pestle or a zip-top bag and rolling pin both work.
Cognac: turn off the heat before adding it (safety first!). Skip it by using a little extra stock plus 1 teaspoon apple cider vinegar.
Sauce thickness: stop simmering when it coats the back of a spoon. It thickens more in the oven.
Make ahead: sear the leeks and make the sauce up to 1 day ahead. Heat up the sauce again before pouring over the leeks and baking.
Storage: refrigerate leftovers up to 3 days. Reheat covered at 350°F/175°C for 15 to 20 minutes, uncovering at the end to re-crisp. Not recommended for freezing.