Cauliflower
Cauliflower is a high-volume, low-calorie food with very little taste, so they've become a popular addition for "hidden veggie" meals. Some add them to mac and cheese by boiling them, blending them, and mixing them into the sauce. They are not entirely undetectable, but if you want more veggies without sacrificing your cheese sauce, give it a try.
There is also no shortage of "cauliflower crust" recipes for things like breadsticks and pizza. To make a cauliflower crust, Boil one head cauliflower, drain, and set it into a kitchen towel. Squeeze out as much moisture as you possibly can into the sink. Then, in a bowl, mix the cauliflower with 1 egg, 1/2 cup of parmesan cheese, salt, pepper, and any other desired seasonings. Spread it out flat onto a baking sheet and bake at 350 degrees until crust is golden brown and set. This will give you a basic cauliflower crust that you can then top with whatever you'd like.
Mushrooms
Mushrooms are a delicious, nutritious addition to any meal, and their naturally meaty texture and umami taste make them super easy to hide in any meal with ground beef. Bolognese, meatballs, sloppy joes, burgers, the options are limited only by your imagination.
All you need to do is chop the mushrooms very finely and add to your ground beef mix. If you're really concerned about the veggies being detectable, try grinding them up in a food processor. Start by adding 1/4 of the amount of beef and see if you'd like to add more.
Keep in mind that mushrooms shrink quite a bit when they are cooked, so if it looks like an overwhelming amount, it may not be by the time you're finished.
