Turn the NInja Foodi on high sear/sauté. Add the butter and allow it to melt. Don't let it brown, so if it is starting to brown reduce your heat to medium.
Add in the flour and stir to combine. You should have a loose paste. Cook for 2 minutes. This is the roux and the base of the cream sauce. Reduce the heat to low.
Slowly add in the milk, about ½ cup at a time and stir to combine with the roux. Add in enough milk to have a smooth, thin cream sauce. It will take between 2-2½ cups of the milk depending on how much the flour will absorb. You can test the sauce by scraping along the bottom of the pot and if it separates for more than a few seconds, you want to add a bit more milk.
Add in the salt and nutmeg and stir.
Add in 1 cup of the grated parmesan cheese and reserve the remaining ½ cup for the topping. Stir until the cheese has completely melted and you have a smooth cheese sauce.
Transfer the cheese sauce to a medium size bowl and set aside for later. Clean the inner pot.
Baked Ziti
Turn the Ninja Foodi on high sear/sauté. Remove the sausage from the casing and add to the pot. Add in the ground beef and break the beat up into small chunks.
Cut the stem end off of the bulb of garlic and remove the individual cloves. Cut the harder end of each clove that was attached to the root end and then smash the clove with the flat side of chef's knife to remove the paper. Add all the garlic cloves to the pot.
Sauté the meat and garlic until the meat is about 75% done. This will take 5-10 minutes.
Add in the 2 teaspoons salt, 1 teaspoon of basil, and ½ teaspoon of black pepper. Stir to combine.
Stir in the ziti noodles into the meat mixture. Add in the beef stock and stir. Press the noodles under the liquid as much as possible.
Pour the marinara sauce on top and DO NOT STIR. This is very important to prevent the water/burn notice.
Place the pressure lid on and turn the valve to seal. Pressure cook on high for 3 minutes. When the time is up, allow the pot to natural release the pressure for 5 minutes and then manually release the remaining pressure.
Remove the lid and don't freak out! Yes, it looks soupy. Yes, it looks like some of the noodles aren't fully cooked. Trust me, it will be just fine.
Stir the pasta mixture to break up any clumps and like magic everything will thicken up and look beautiful. Any underdone pasta will finish cooking with the residual heat and the baking time.
Smooth out the top so that pasta is as flat as possible and spoon on the cheese sauce. I start at the edges and then smooth it all over the top. You want all the pasta covered with the cheese sauce and not have the cheese sauce mix with the red sauce if possible.
Lower the crisping lid and select the bake/roast function on 325°f/160°C and bake for 10-15 minutes. Check at 10 minutes and if you see one area browning more than others, you can rotate the pot. If it looks like it's getting too brown, lower the heat. Sometimes 10 minutes is all you need for the cheese sauce to lightly brown and set. (see notes below if you don't have a crisping lid)
Sprinkle on the remaining ½ cup shredded parmesan cheese and bake at the same temperature for 3-5 minutes. Let sit for at least 15 minutes before serving.
Garnish with fresh basil strips or chopped fresh basil. Serve & Enjoy!
Instant Pot without a Crisping LidOnce you are done pressure cooking the pasta in the sauce and stirring it, transfer the pasta and sauce to a large (at least 4qt) casserole dish or two smaller casserole dishes. Top with the cheese sauce and bake in a preheated oven at 375℉/190℃ for 10-15 minutes. Add additional cheese and bake another 3-5 minutes. Let sit 15 minutes and garnish with fresh basil if desired.