Spray an 8-quart crock pot with nonstick cooking spray.
In the crock pot, add in ham, macaroni, milk, evaporated milk, 3 cups of shredded cheddar cheese, Velveeta, butter, salt, pepper, and ground mustard. Mix together thoroughly.
Set the crock pot to the low heat setting and cook for 2.5 to 3 hours, or until the macaroni becomes tender. Stir the mixture every 30 minutes to ensure it cooks evenly and doesn't stick to the edges.
Keep an eye on the consistency. If it starts to look done (the noodles are cooked) and thickened (but still a little loose) it's time to add the additional 1 cup of shredded cheese on top. Cover the slow cooker with the lid for approximately 5 minutes to melt the cheese.
Once the cheese has melted, it is ready to serve.
Notes
Please refer to my FAQ’s (Frequently Asked Questions) and ingredient list above for other substitutions or for the answers to the most common questions.
It's totally normal if the cheese sauce starts to separate by the end. Just give it a good stir.
I have not tested this recipe in anything smaller than an 8 quart slow cooker. You could probably do it in a 6 quart but I would keep an eye on the timing as it could take longer and may need more occasional stirring.
In addition, this recipe was designed for the slow cooker only. I cannot give instructions on how to make it another way.
Store leftovers in a container in the fridge for up to 4 days or in the freezer for up to 3 months.