- 2 tablespoons unsalted butter
- 2 tablespoons all-purpose flour
- 1 1/4 cups whole milk, warmed
- Coarse salt and freshly ground pepper
- 12 small fingerling potatoes (or 4 to 5 ounces other small waxy potatoes), cooked until tender, smashed
- 2 tablespoons extra-virgin olive oil
- 4 slices (3/4 inch thick) day-old <a href="/how-to/tartine-country-bread">Tartine Country Bread</a>
- 4 thick slices smoked ham
- 8 slices Gruyere cheese (4 ounces)
- Make the bechamel: Melt butter in a heavy saucepan over medium heat. Add flour, and whisk until mixture bubbles slightly, but has not started to brown, about 2 minutes. Whisk in milk. Bring to a boil to thicken. Season with salt and pepper. Remove from heat.
- Make the croque-montagnarde: Preheat oven to 425 degrees. Toss potatoes with oil. Spread 1/4 cup bechamel onto each slice of bread, and top with 1 slice of ham, some potatoes, and 2 slices of cheese. Bake on a baking sheet until cheese is golden and bubbling, 12 to 14 minutes (start checking often after 8 minutes, and rotate sheet as needed for even browning).
Bechamel can be refrigerated for up to 3 days. Press plastic wrap directly onto the surface to prevent a skin from forming. Reheat before using.