Preheat oven to 400˚F (200˚C). Cook macaroni according to package directions; drain, reserving 1/4 cup (60 mL) boiled pasta water.

Meanwhile, melt 2 tbsp (30 mL) butter in large skillet set over medium heat; cook garlic, for about 1 minute or until fragrant.

Stir in flour; cook for 1 to 2 minutes or until smooth. Slowly whisk in milk. Bring to a boil, whisking constantly. Reduce heat to medium-low; simmer for 8 to 10 minutes or until mixture is slightly thickened. Stir in 1/4 tsp (1 mL) of both salt and pepper. Remove from heat. Stir in half of the cheese until melted.

4Meanwhile, melt remaining butter in separate skillet set over medium heat; cook leeks, and remaining salt and pepper for 3 to 5 minutes or until slightly softened.

Stir together chicken and barbecue sauce. Stir macaroni into cheese sauce until well coated; fold in chicken mixture and leeks. If sauce is too thick, stir in enough of the reserved boiled pasta water for desired consistency.

Transfer to a greased 13- x 9-inch (3.5 L) baking dish. Sprinkle with remaining cheese. Bake for 15 to 20 minutes or until golden and bubbly. Sprinkle with chives. Let cool for 10 minutes before serving.

Tips:
• For an easier and quicker preparation, use rotisserie cooked chicken.
• Use your favourite barbecue sauce to suit your taste: Try classic style, smoky or spicy.