Preheat oven to 375 ̊F. Butter an 8-inch square (11⁄2 quart) baking dish or pan (or six 8-ounce ramekins). Set aside. Fill a 4to 5-quart pot about 3⁄4 full with water and add 1 tablespoon of the salt. Bring to a boil and add the pasta. Cook, stirring once or twice, until tender but firm, about 4 minutes, and drain. Reserve the pot.
While the pasta is cooking, in a medium skillet, melt 2 tablespoons butter over medium heat. Turn off the heat and add the breadcrumbs and dry Jack. Stir to combine, and set aside.
Using the same pot you used to cook the pasta, melt the remaining 2 tablespoons butter over medium heat. Slowly whisk in the flour and stir constantly until a paste forms, 30 to 45 seconds. Continue stirring for 1 to 2 minutes more, or until the mixture starts to darken slightly and smell a bit nutty. Slowly whisk in the milk, cream and remaining 1 teaspoon salt and cook until the mixture starts to thicken and is just beginning to bubble around the edges, 5 to 7 minutes. It should be thick enough to coat the back of a wooden spoon. Add the Toma, goat cheese, cayenne and nutmeg and stir until the sauce is smooth but not too runny. It should be similar in texture to cake batter. If it’s soupy, continue cooking until it thickens.
Add the pasta and stir to combine. Pour into the prepared baking dish. Sprinkle with the breadcrumb mixture. Place the dish on a rimmed baking sheet and bake for 15 minutes. Remove the casserole from the oven and distribute the Mt. Tam over the top. Return to the oven and cook for 15 minutes longer or until the Mt. Tam has softened and the crumbs are golden brown. Let cool for 15 minutes before serving.
From Mac & Cheese, Please! by Laura Werlin (Andrews McMeel Publishing, 2012)