Ingredients:

  • 2 tbsp unsalted butter, for roux
  • 2 tbsp all-purpose flour
  • 1 cup whole milk, warmed
  • 1/2 cup Gruyère cheese, freshly grated, for Mornay sauce
  • 1/2 tsp lemon zest, finely grated
  • 1/4 tsp nutmeg, freshly grated
  • 1 pinch kosher salt
  • 1 pinch white pepper
  • 4 thick slices sourdough bread
  • 2 tbsp unsalted butter, softened, for toasting bread
  • 5 oz smoked salmon, cold-smoked
  • 1 tbsp fresh dill, chopped
  • 1 tsp capers, drained and patted dry
  • 1/2 cup additional Gruyère cheese, grated, for filling

Instructions:

  1. Melt 2 tablespoons of unsalted butter in a small heavy bottomed saucepan over medium heat. Let it sizzle until the foaming subsides.
  2. Create the roux. Whisk in 2 tablespoons of all purpose flour. Cook for 1–2 minutes until the mixture smells nutty but remains pale. Note: Don't let it brown, or the sauce will taste toasted rather than creamy.
  3. Whisk in milk. Slowly stream in 1 cup of warmed whole milk while whisking constantly. Continue cooking until the sauce is thick enough to coat the back of a spoon.
  4. Finish the Mornay. Remove from heat. Fold in 1/2 cup Gruyère, 1/2 teaspoon lemon zest, and 1/4 teaspoon nutmeg. Add a pinch of salt and white pepper. Set aside.
  5. Toast the bread. Lightly butter one side of each of the 4 sourdough slices with softened butter. Place in a skillet over medium heat, butter side down, until the surface is pale gold. Remove bread from skillet.
  6. Layer the base. Spread a generous layer of the Mornay sauce on the toasted side of two slices.
  7. Add the fillings. Layer 5 ounces of cold smoked salmon over the sauce. Sprinkle with 1 tablespoon of fresh dill, 1 teaspoon of capers, and 1/2 cup of additional Gruyère cheese.
  8. Close the sandwiches with the remaining two bread slices, ensuring the untoasted side faces inward. Lightly butter the outer faces of the assembled sandwiches.
  9. Griddle the sandwiches in the skillet over medium heat until both sides are mahogany-colored and the cheese is fully melted.