Chicken Croque Monsieur Recipe

Prepare marinade

In a shallow bowl or zip-top bag combine 2 tbs olive oil, chopped parsley, thyme, minced rosemary, minced garlic, lemon juice, 1 tsp salt and 1 tsp black pepper. Whisk or shake to emulsify.

Marinate chicken

Pound each chicken breast to an even thickness of about 1/2" (use a meat mallet or rolling pin between plastic). Add the chicken to the marinade, coating thoroughly. Refrigerate for at least 30 minutes and up to 4 hours.

Cook chicken

Heat a large skillet over medium-high heat. Add a light drizzle (about 1 tbs) of olive oil. Sear the marinated chicken 3-4 minutes per side until golden and an instant-read thermometer reads 160°F (71°C). Remove to a plate and let rest 5 minutes (carryover will bring to 165°F). Slice thinly on a bias for assembly.

Make roux

In a small saucepan over medium heat melt 2 tbs butter. Once foaming, whisk in 2 tbs flour and cook, whisking constantly, 1 to 1.5 minutes to remove raw flour taste but not brown.

Add milk

Gradually whisk in 1 cup cold whole milk in a steady stream to avoid lumps. Continue whisking and bring to a gentle simmer. Cook until the sauce thickens and coats the back of a spoon, about 3-5 minutes.

Finish Mornay

Remove from heat and whisk in 1 cup grated gruyère and 2 tbs Parmesan a handful at a time until smooth. Stir in 1 tsp Dijon mustard, a pinch of nutmeg, 1/2 tsp salt and 1/4 tsp white or black pepper. Taste and adjust seasoning. Keep warm; if it becomes too thick, whisk in up to 1-2 tbs milk to loosen.

Prepare bread

Preheat oven to 425°F (220°C). Lightly butter one side of each sourdough slice with the softened butter. If using Dijon mustard, spread 1/2 tsp on the unbuttered side of two slices (these will be the bottom slices).

Layer sandwich

Place two buttered-side-down slices on a baking sheet. Top each with an even layer of sliced cooked herb chicken (divide between sandwiches), then a generous sprinkling (about 1/2 cup per sandwich) of thinly sliced or grated gruyère. Spoon about 2-3 tbs of warm mornay sauce over the cheese layer on each sandwich. Top with the remaining bread slices, buttered side up.

Bake

Bake in the preheated oven 6-8 minutes, until the bottoms are golden and the cheese starts to melt. Remove baking sheet, spoon the remaining mornay sauce over the top of each sandwich and sprinkle remaining gruyère over the sauce.

Broil to finish

Switch oven to broil on high and move the baking sheet to the top rack. Broil 1-2 minutes, watching closely, until the top is bubbling and golden-brown. Remove from oven.

Rest and serve

Let sandwiches rest 2 minutes, garnish with chopped chives or parsley, slice in half, and serve hot.