Step 1

Spray or butter your baking dish and set off to the side. (I used a 12¼" x 8¾" dish.)

Step 2

Cook the pasta according to the package*.

Step 3

*I salt the water just before adding the pasta. *I suggest cooking it 2 minutes less than the shortest recommended time. (For example my cellentani said "Cook 11-12 minutes for al dente" so I cooked it for 9 minutes.) This might seem undercooked, but the noodles will soften more when you add the sauce and put it in the oven, so this avoids soggy noodles that fall apart.

Step 4

When cooked, drain the pasta and add it to a large bowl, set aside.

Step 5

In a medium pot, make the roux by melting the butter then adding the flour. Stir with a whisk to combine and cook about 3 minutes until the flour is a little toasted/ lightly browned.

Step 6

Slowly whisk the milk into the roux a little bit at a time, being sure to fully whisk away any lumps before adding more milk. (Once you've slowly added about half the milk, you should be able to add the rest of the milk all at one time while maintaining a smooth, non-lumpy sauce.)

Step 7

Bring the sauce to just below boiling, stirring constantly, to thicken it for about 5-10 minutes.

Step 8

Add the cheddar and havarti to the large bowl of pasta, stirring to combine.

Step 9

Transfer the pasta/cheese mixture into your baking dish.

Step 10

Pour the piping-hot sauce (so it melts the cheese) evenly over the pasta/cheese mixture in the baking dish.

Step 11

Top evenly with the breadcrumbs and parmesan.

Step 12

In your oven, arrange a rack to be on the second-closest level to the broiler. Turn broiler on low.

Step 13

Place casserole under broiler and close the oven door so the whole casserole stays heated while the top browns. Watch carefully to avoid burning, about 10-15 minutes depending on your oven.

Step 14

Spray or butter your baking dish and set off to the side. (I used a 12¼" x 8¾" dish.)

Step 15

Cook the pasta according to the package*.

Step 16

*I salt the water just before adding the pasta. *I suggest cooking it 2 minutes less than the shortest recommended time. (For example my cellentani said "Cook 11-12 minutes for al dente" so I cooked it for 9 minutes.) This might seem undercooked, but the noodles will soften more when you add the sauce and put it in the oven, so this avoids soggy noodles that fall apart.

Step 17

When cooked, drain the pasta and add it to a large bowl, set aside.

Step 18

In a medium pot, make the roux by melting the butter then adding the flour. Stir with a whisk to combine and cook about 3 minutes until the flour is a little toasted/ lightly browned.

Step 19

Slowly whisk the milk into the roux a little bit at a time, being sure to fully whisk away any lumps before adding more milk. (Once you've slowly added about half the milk, you should be able to add the rest of the milk all at one time while maintaining a smooth, non-lumpy sauce.)

Step 20

Bring the sauce to just below boiling, stirring constantly, to thicken it for about 5-10 minutes.

Step 21

Add the cheddar and havarti to the large bowl of pasta, stirring to combine.

Step 22

Transfer the pasta/cheese mixture into your baking dish.

Step 23

Pour the piping-hot sauce (so it melts the cheese) evenly over the pasta/cheese mixture in the baking dish.

Step 24

Top evenly with the breadcrumbs and parmesan.

Step 25

In your oven, arrange a rack to be on the second-closest level to the broiler. Turn broiler on low.

Step 26

Place casserole under broiler and close the oven door so the whole casserole stays heated while the top browns. Watch carefully to avoid burning, about 10-15 minutes depending on your oven.