Tip 2. You May Have to “Par-Cook” Vegetables That Take Longer to Finish.
“Par-cook” is chef speak for partially cooking something. If you want to mix and match ingredients that cook at different rates, you need to ensure that everything finishes at the same time. That’s where par-cooking comes into play. If you give ingredients that are slower to cook a head start—such as potatoes, carrots or other root vegetables—and then add them to a casserole that also has quicker-cooking veggies, such as broccoli or green beans, they’ll be finished around the same time. You can par-cook vegetables by steaming, boiling and even roasting. Just remember not to cook them all the way. They’ll finish cooking in the casserole.