I got the recipe from a Weber recipe book I got a few years ago but modified it to replace ham with bacon, eliminated green onions & thyme. Here's the recipe from the book:
3-4 medium poblano chiles, about 3/4 pound
1/2 pound baked ham, sliced about 1/3 inch thick
6 scallions, including the green tops
Extra-virgin olive oil
4 tablespoons unsalted butter plus a little extra for
buttering the baking dish
4 tablespoons all-purpose flour
1 quart whole milk
4 cups (about 12 ounces) grated Monterey Jack
1/4 cup grated Parmigiano-Reggiano cheese
3/4 teaspoon kosher salt
1/4 teaspoon freshly ground black pepper
10 ounces large elbow macaroni
1/2 cup fresh bread crumbs
2 teaspoons finely chopped fresh thyme
1. Lightly coat the chiles, sliced ham, and green onions with oil. Grill the poblano chiles over direct medium heat (350° to 450°F), with the lid closed as much as possible, until evenly charred on all sides, 8 to 10 minutes, turning as needed. At the same time, grill the ham and scallions over direct medium heat until lightly charred, 4 to 5 minutes, turning once or twice. Remove the chiles, ham, and scallions from the grill and let cool. Peel away the charred skins from the chiles. Remove and discard the stems and seeds. Roughly chop the chiles. Dice the ham into 1/3-inch cubes. Thinly slice the scallions crosswise and discard the root ends.
2. In a large saucepan over medium heat, melt the butter. As it starts to sizzle, whisk the flour into the butter to form a paste. Cook this mixture until it starts to brown, 3 to 4 minutes, stirring occasionally. Add the milk while whisking to keep lumps from forming. Raise the heat to medium-high. Gradually add 3 cups of the Monterey Jack cheese, all the Parmigiano-Reggiano cheese, the salt, and the pepper. As the cheese melts into the sauce and it begins to boil, lower the heat to a simmer. Cook for 4 to 5 minutes. Remove the cheese sauce from the heat and pour into a buttered 2 1/2- to 3-quart baking dish
3. Cook the macaroni in salted boiling water for 3 minutes less than the cooking time recommended on the package. Drain the macaroni and add it to the baking dish, mixing it with the cheese sauce. Add the chiles, ham, and scallions. Mix well.
4. In a small bowl mix the bread crumbs with the remaining 1 cup of Monterey Jack cheese and the thyme. Top the pasta with the bread crumb mixture and gently press it into the surface.
5. Place the baking dish over indirect medium heat and cook, with the lid closed as much as possible, until the mac and cheese is golden brown on top, 25 to 30 minutes. Wearing insulated mitts, remove the dish from the grill let cool slightly. Serve warm