Spray the inside of the crockpot with cooking spray. Add the uncooked macaroni, cubed Velveeta, whole milk, evaporated milk, butter, garlic powder, onion powder, salt, and pepper to the crockpot. Stir to combine all ingredients well.
Cover and cook on LOW for 2 hours, stirring every hour to prevent sticking. Different crockpots heat differently, so check pasta tenderness at 1 hour 45 minutes.
Once pasta is tender, stir in the shredded cheddar cheese until melted and well combined. If mixture seems too thick, add additional warm milk, 1/4 cup at a time, until desired consistency is reached.
Serve immediately while hot and creamy. Mac and cheese will continue to thicken as it stands.
Switch crockpot to WARM setting.
Notes
Pro Tip:
For the creamiest macaroni texture, make sure to check for al dente doneness around the 1-hour and 45-minute mark, as cooking times can vary by slow cooker. For the best results, use freshly shredded cheese instead of pre-shredded for a smooth, melt-in-your-mouth cheese sauce.