Bring generously salted water to boil in a large pasta pot. Add macaroni and cauliflower florets and cook according to pasta package directions. Drain and set aside
Melt butter in a large saucepan over medium heat.
Add flour, salt and pepper and whisk together vigourously for about 2 minutes
Slowly pour in milk, stirring constantly.
Bring to a boil and stir constantly for about 2 minutes.
Reduce heat and cook for about 6 more minutes, stirring constantly, until sauce thickens.
Add shredded cheddar by handfuls and simmer an additional 5 minutes, until cheese melts.
Remove from heat and macaroni/cauliflower to the saucepan and toss to coat with the cheese sauce.
Transfer mixture to a buttered baking dish and sprinkle evenly with breadcrumbs.
Bake for 20 minutes until the top is golden brown.
Recipe by Three Hungry Boys at https://www.threehungryboys.com/2016/01/21/cauliflower-mac-cheese/