I recommend reading entire recipe and having everything measured out and cheese shredded before beginning
Don’t use pre shredded cheese, shred it yourself
In a large sauce pan bring about 3quarts of water to a boil and salt to water, add elbow noodles and boil using instructions on the box or until noodles are al dente. Strain noodles in a colander and set aside.
Next make the roux. In a large saucepan (needs to be large enough to add all ingredients including cooked noodles) add 3 Tbsp of butter over low/medium heat. Once butter is melted, add 3 Tbsp flour and stir constantly for about 2 minutes to cook flour (don’t burn it). Slowly whisk in milk and half & half, continue to whisk, increase heat to medium. Add 3/4 tsp ground mustard, 1/2 tsp onion powder, 1/4 tsp paprika, 1/2 tsp minced garlic. Cook for 3-4 minutes until mixture starts to thicken. Be careful not to burn or overheat. After mixture is slightly thickened turn off heat, add all cheese and mix until cheese is melted and sauce is creamy. Add cooked elbow macaroni noodles, mix well.
Spray a casserole dish with Pam cooking spray, Pour Mac and cheese into casserole dish.
Melt 2 Tbsp of butter in a microwave safe bowl, add the rest of the topping ingredients and mix well. Use hands to sprinkle topping over Mac and Cheese
Bake at 375 degrees for about 15 minutes until topping is slightly browned and Mac and cheese is bubbly