Place a skillet over medium-low heat. Add butter to the skillet and let it melt. Clean and cut your leeks into 5 cm or 2-inch chunks. Add them to the skillet. Increase the heat to medium-high. Season with salt and pepper. Add whole grain dijon mustard, stir to combine. Pour in the dry white wine (for example Pinot Grigio) and water. Leave to simmer over low heat for 15 - 20 minutes.TipYou can substitute white wine with 1 tbsp of lemon juice.
sear the cod
Pat dry your cod fillets. Season with salt and pepper on both sides. Wrap each fillet tightly in a couple of slices of pancetta. Get a non-stick pan. Place it over medium-high heat. Add 1 tbsp of olive oil. Place each pancetta-wrapped cod fillet into a hot (but not smoking) pan seam side down. Sear each fillet for 2 minutes on each side.
Bake the cod and serve
Transfer the seared cod to a baking sheet lined with parchment paper (or use an oven-safe pan). Place in the preheated oven. Bake for 6 - 8 minutes at 200 °C / 400 °F. Remove from the oven. Remove the leek sauce from the heat, stir 1 tbsp of cold butter into the hot leek sauce, let the butter melt, then serve the cod with the silky, mustardy butter leek sauce immediately. Optionally sprinkle with chopped roasted hazelnuts. Enjoy.TipIn the oven, bake for 6 - 8 minutes if you're using a cod fillet that's about 2 cm or 1-inch thick, otherwise adjust the cooking time, depending on the thickness of your fillet. The cod fillet is cooked, when it flakes easily with a fork. Make sure not to overcook it, it cooks fast.