01 - Preheat the oven to 375°F. Line a baking sheet with parchment paper.
02 - Cook the elbow macaroni in salted boiling water according to package directions until al dente. Drain and set aside.
03 - In a medium saucepan, melt butter over medium heat. Whisk in flour and cook for 1 minute. Gradually add milk, whisking constantly until the mixture thickens, about 2–3 minutes.
04 - Remove saucepan from heat and stir in cheddar cheese until melted and smooth. Season with salt and pepper.
05 - Fold the cooked macaroni into the cheese sauce until fully coated.
06 - Slice each hot dog sausage lengthwise down the center, being careful not to cut all the way through, creating a pocket.
07 - Fill each hot dog with a generous spoonful of mac and cheese.
08 - Place the stuffed hot dogs in buns and arrange on the prepared baking sheet. Sprinkle each with extra shredded cheddar if desired.
09 - Bake for 10–12 minutes, until the cheese is bubbly and the hot dogs are heated through.
10 - Garnish with chives and crispy fried onions before serving, if desired.