It helps to know: This recipe requires an 8 by 12-inch gratin dish.

• To make a béchamel sauce, bring the milk to a simmer in a small pot on low heat.
• In a second small pot on low heat, melt 2 tablespoons of the butter.
• Add the flour to the butter to make a roux, whisking continuously to prevent it from burning.
• Continue whisking until the roux turns a light yellow color, about 10 minutes.
• Slowly pour the simmering milk into the roux, a couple of tablespoons at a time.
• Whisk continuously on low heat until it thickens to a syrupy consistency.
• Season with a couple generous pinches each of salt and pepper.
• Remove the pan from the heat and set aside.
• To prepare the endives, peel off the outer leaves until you’re left with the firm and mostly white hearts.
• Trim and discard the bottom stem, being careful not to trim too high or they’ll fall apart.
• Melt the remaining 2 tablespoons butter in a large pot on medium heat.
• Working in batches, set the endives in the melted butter and turn until they’re fully browned on each side, about 10 minutes total.
• Set the browned endives aside as you brown the remaining endives.
• Preheat your oven to 375°F.
• Return the endives to the pan.
• Turn the heat to low and add the lemon juice, 3 tablespoons water, and a pinch of salt.
• Cover the pan with the lid slightly ajar to allow steam to escape, and simmer until the endives are cooked through, about 20 minutes.
• Transfer to a plate and set aside to cool to room temperature.
• Roll each endive in a ham slice like a blanket.
• Whisk out any lumps from your béchamel, then spread a spoonful evenly across the bottom of your gratin dish.
• Set the ham-wrapped endives in one layer on top of the béchamel.
• Scoop the rest of the béchamel on top, then top with the Gruyère.
• Place the dish on a baking sheet to save you from a mess if it bubbles over.
• Bake until everything is heated through, caramelized, and bubbly, about 45 minutes.
• Serve immediately.