A croque monsieur is basically a gooey cheese sandwich stacked with salty ham and slathered with creamy sauce. This version subs in prosciutto and throws an egg into the mix, turning the croque monsieur into a croque madame (don’t mind if we do). Let’s just say this next-level sandwich is a winner no matter your French.
2 tablespoons unsalted butter, divided
3 ounces frisée
6 ounces green beans
⅛ ounce chives, divided
1 tablespoon flour
4 slices white bread
4 slices Swiss cheese
8 ounces milk
2 teaspoons Dijon mustard
2 ounces prosciutto
2½ tablespoons honey
2 baking sheets
8″ medium pot
10″ medium nonstick pan
Using your hands will warm the butter slightly, so it combines with the flour more easily.
Before cheese is added to the sauce, it is technically a béchamel; after adding cheese, it’s a Mornay sauce.
Before being topped with a fried egg, the sandwich is technically a croque monsieur; afterwards, it’s called a croque madame. Feel free to omit the egg if you prefer—but it’s one of our favorite parts!
Preheat oven to 450°F. Set butter aside to soften at room temperature. Rinse all produce. Trim ½ inch of dark green tops off frisée, trim and discard tough stem, and tear into bite-size pieces. Trim and discard ends of green beans, then transfer to a baking sheet and toss with 1 tablespoon olive oil, ¼ teaspoon salt, and pepper. Thinly slice chives. Halve lemon. Set aside 2 slices Swiss cheese for Step 4; roughly chop remainder for Step 3.
In a small bowl, combine flour and 2 packets softened butter and, using your fingers, knead together until fully blended to form a smooth paste (see Recipe Tip). On a separate baking sheet, arrange bread slices in a single layer. Spread remaining butter over both sides of bread slices, dividing evenly. Transfer to oven and toast until golden, 5 minutes. Then, remove from oven and set aside to cool.
Heat milk, ½ teaspoon salt, and pepper as desired in a medium pot over medium-high heat. Bring to a boil, whisking, then whisk in beurre manié until fully dissolved, 30 seconds. Reduce heat to medium and whisk until sauce is thickened, 3-4 minutes more (see Recipe Tip). Remove from heat and whisk in chopped Swiss cheese. Transfer baking sheet with green beansto oven and roast until tender, 8-10 minutes.
While green beans roast, still on baking sheet, spread mustard evenly over 1 side of 2 bread slices. Layer remaining bread slices with sliced Swiss, then prosciutto, then half of Mornay sauce. Finish with mustard bread slices, mustard-side down. Spread remainingMornay sauce over tops of sandwiches. Transfer to oven (with green beans) and bake until tops are golden brown, about 8 minutes.
While sandwiches bake, heat 1 tablespoon olive oil in a medium nonstick pan over medium heat. When oil is shimmering, crack 2 eggs into pan (see Recipe Tip). Season with ¼ teaspoon salt and pepper. Fry until whites are set but yolks are still runny, 2-3 minutes. Remove pan from heat. In a medium bowl, whisk together ½ packet honey, half of chives, juice of 1 lemon, 2 tablespoons olive oil, ¼ teaspoon salt, and pepper.
Add roasted green beans and frisée to bowl with dressing, toss to coat, and transfer to serving plates. Add sandwiches to plates with green beans, then top with fried eggs. Sprinkle remaining chives over prosciutto croque madames and enjoy! Save remaining honey to sweeten a cup of tea.
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