Bring a large pot of water to a boil over high heat; generously salt water and return to a boil. Add pasta and cook until al dente according to package directions, 7 to 8 minutes. Drain and set aside.
In a medium saucepan, heat milk and heavy cream over medium-low heat until warmed through.
Meanwhile, in a large saucepan, melt butter over medium heat. Add flour and stir until well combined, 5 to 6 minutes, taking care not to let the mixture brown. Slowly add milk mixture, whisking until well combined. Bring to a simmer and let cook 15 minutes.
Whisk in cheese until melted and sauce has thickened; remove from heat. Using an immersion blender, blend mixture until smooth; season with 1 teaspoon salt and pepper. Stir in pasta until fully coated; set macaroni and cheese aside.
Preheat a grill pan over medium-high heat.
Grill hot dogs until cooked through, 5 to 7 minutes. Transfer hot dogs to buns, and top each with about 1/3 cup reserved macaroni and cheese. Serve immediately.