Heat a large pan or skillet over medium-high heat and cook ground beef, breaking it up as it cooks, until browned. Season generously with salt and pepper and garlic powder.
Drain fat, then wipe out skillet with a paper towel. Melt butter in skillet, then whisk in flour. Cook roux for 2-3 minutes, or until golden brown, then whisk in whole milk. Season with salt and pepper, then remove from heat and refrigerate until ready to use.
Place beef, along with onion, carrot, celery and potatoes in slow cooker and cover with chicken broth. Season with basil and parsley, the cover and cook on high for 3-4 hours, or until potatoes are tender.
Stir in refrigerated roux mixture, then add in cubed velveeta. Cover again and cook for another 30 minutes, or until cheese is melted and soup is thick and smooth.
Serve hot, topped with cheese and bacon bits. Enjoy!