This is how my mac and cheese soup turned out after following (a combination of) the top recipes I liked. You’ll probably notice that, for a soup, it’s not as liquidy as it should be. You’re right. After cooking it had a fair amount of liquid; I let it rest to play with my daughter, and about half an hour later, the paste had absorbed most of the stock. This wasn’t mentioned in all of the recipes, so let me make it clear: either make enough broth to keep it soup-like, or serve it immediately after cooking.
But nevertheless, I loved it. For the cheese, I used mainly used cheddar as well as low-fat cream cheese (as I ran out of cheddar). I put the broth in the blender to make it smoother, though next time I would leave about half unblended to leave some vegetable chunks. For toppings, I used oven-roasted tomatoes as well as (not in the picture) toasted breadcrumbs with parmesan, basil, and olive oil. I would reduce the flour the next time to thin out the soup. I served this with fried chicken for my daughter (yeah, I should’ve baked it; but it was leftover from last night’s dinner); and buffalo chicken wings for myself (also leftover).