Preheat oven to 400˚F (200˚C). Grease 24 nonstick mini muffin cups. Cook pasta according to package directions; drain, reserving 1/4 cup (60 mL) cooking liquid.
Meanwhile, melt butter in large skillet set over medium heat; cook garlic for about 1 minute or until softened. Sprinkle flour over top; cook, stirring, for 2 to 3 minutes or until smooth.
Slowly whisk in milk; bring to boil, whisking constantly. Reduce heat to medium-low; cook, stirring constantly, for 3 to 5 minutes or until thickened slightly. Stir in mustard, salt and pepper.
Remove from heat; stir in 1 1/2 cups (375 mL) cheese until melted. Stir in pasta, adding enough of the cooking liquid for desired consistency. Let cool slightly.
Spoon into prepared muffin cups. Sprinkle with remaining cheese; bake for 12 to 15 minutes or until golden and bubbly. Let stand for 10 minutes; remove from pan.
Tip: Alternatively, for Mac ‘n Cheese cups, bake in standard muffin tins.