Ham and Cheddar Cheese Gratin

Preheat an oven to 400°F. Butter a 1 1/2-quart gratin dish or other round or oval shallow baking dish.

In a small sauté pan over medium heat, melt the butter. When the foam subsides, add the onion and celery and sauté until soft and translucent, about 3 minutes. Add the ham and sauté until heated through, about 2 minutes. Mix in the tarragon and season with pepper. Scatter the ham mixture over the bottom of the prepared dish. Set aside.

To make the sauce, in a heavy saucepan over medium-high heat, melt the butter. Add the flour and cook, stirring constantly, for 2 minutes without browning the flour, adjusting the heat as needed. Remove from the heat. Add the hot milk all at once and whisk vigorously to prevent lumps from forming. Return the pan to the heat and cook, stirring constantly, until thickened, about 2 minutes. Season with the tarragon, mustard, nutmeg, cayenne pepper and black pepper. Stir in the cubed cheese. Taste and adjust the seasonings.

Cut the hard-cooked eggs in half lengthwise; set 6 halves aside. Coarsely chop the remaining halves and stir into the warm sauce. Pour all but about 1/4 cup of the sauce over the ham mixture. Then nest the reserved egg halves, yolk sides up, in the sauce, spacing them evenly so they indicate the center of a serving. Whisk 1 to 2 Tbs. cream into the reserved sauce to thin it, then spoon over the eggs. Scatter the shredded cheese over the top.

Bake until the sauce is bubbling and the surface is golden brown, 10 to 12 minutes. Serve directly from the dish