
Cook the noodles. Bring a large pot of salted water to a boil and cook macaroni noodles according to package directions and drain.
Make the sauce. Heat a 12 inch cast iron skillet over medium heat. Melt 1/2 cup of butter and whisk in the flour until a smooth, thin paste forms. Then whisk in the mustard powder.Carefully pour in the half and half and bring the mixture up to a boil while whisking. Reduce the heat and whisk in the cream cheese until smooth. Whisk in the cheddar cheese and Gouda cheese and stir until melted.
Combine the noodles and sauce. Turn off the heat and pour in the cooked macaroni noodles. Stir gently until the noodles are coated by the cheese sauce. Serve immediately.