Crisp on the outside and gooey on the inside, these mac and cheese delights are baked in your doughnut pan -- a gadget you may have used once, then promptly stashed in the far back corner of your cabinet. Shaped like onion rings and served with marinara, these indulgent treats are stuffed with both mac and cheese and a layer of mozzarella -- for extra cheese pulls.
Bring a pot of salted water to a boil. Add the macaroni and cook until al dente, about 6 minutes. Drain and set aside.
Meanwhile, add the crackers to a large bowl and crush into fine crumbs with the back of a measuring cup. Add the breadcrumbs and mix to combine. Coat a 6-cavity nonstick doughnut pan with nonstick spray. Add half of the breadcrumb mixture to the cavities, tilting the pan and gently tapping it to spread around the breadcrumbs so they cover as much of each cavity as possible. It's okay if a few extra breadcrumbs remain at the bottom of each cavity.
Heat the half-and-half and cayenne in a medium saucepan over medium heat until the mixture just comes to a simmer. Continue to simmer over medium-low heat until the half-and-half is reduced by a little more than half, about 2 minutes. Add the cream cheese and stir until melted. Stir in the Cheddar until all of the cheese is melted and the sauce is smooth. Add the macaroni to the saucepan and stir to combine. Season with salt if needed.
Carefully fill each doughnut pan cavity halfway with the macaroni and cheese. Top each with a layer of mozzarella slices, then the remaining macaroni and cheese. Evenly cover each with the remaining breadcrumb mixture and gently pack down each ring with your fingertips. Lightly spray the top of each with nonstick spray.
Bake until the cheese is bubbly and the breadcrumbs are lightly browned and crispy, 7 to 9 minutes. Let rest in the molds until the macaroni and cheese mixture stays together in a ring when you lift it out with the help of a butter knife, 5 to 10 minutes. Serve with marinara sauce.