Step 1

1 Bring a large pot of salted water to a boil over medium-high heat

Step 2

2 Add the pasta and cook according to package directions, leaving it slightly undercooked if the casserole is to be frozen

Step 3

3 Drain and transfer to a large bowl

Step 4

4 Toss with 1 tablespoon of the oil

Step 5

5 Meanwhile, clean and trim the mushrooms and cut them into quarters, or cut them in half if they are small

Step 6

6 Cut the zucchini into 3/4-inch-thick slices, then cut the slices into quarters or halves

Step 7

7 Cut the roasted red peppers into short strips

Step 8

8 Preheat the oven to 350 degrees if you will be serving the dish rather than freezing it

Step 9

9 Lightly grease a shallow 2 1/2-quart casserole or baking dish with olive oil

Step 10

10 Heat the remaining 1 tablespoon of oil in a large skillet over medium-high heat until the oil shimmers

Step 11

11 Add the mushrooms, zucchini, fennel seeds and salt

Step 12

12 Stir-fry the vegetables for 5 to 7 minutes, until they are barely tender

Step 13

13 When they are almost done, add the garlic and cook for a minute or so, stirring, taking care not to burn the garlic pieces

Step 14

14 Transfer the cooked vegetables to the bowl with the pasta, then add the roasted red pepper strips and the pasta sauce

Step 15

15 Taste the mixture and add the crushed red pepper flakes, if desired, for a spicier flavor

Step 16

16 Layer half of the pasta mixture in the prepared casserole or baking dish, then sprinkle it evenly with half of the mozzarella

Step 17

17 Cover with the remaining pasta mixture and top with the remaining cheese

Step 18

18 If the dish is to be served rather than frozen, loosely tent it with aluminum foil

Step 19

19 Bake for 35 minutes, then remove the foil and bake for 10 to 15 minutes, until the casserole is sizzling and the edges of the cheese have browned

Step 20

20 Let it rest for 10 minutes before serving