1poundsliced mushroomI used cremini mushrooms, but any mushroom works
1onionfinely diced
5clovesgarlicfinely minced
2tablespoonchopped fresh thyme leaves
½cupsherryuse vermouth or whatever dry white wine you have if you don't have any sherry
½cupall-purpose flour
4cupswhole milkroom temperature
1cupheavy whipping creamroom temperature
1cupchicken broth
pinchof nutmeg
salt and pepper
pastaI like penne-style, but use what you like/have, cooked just under what the box says - you want a little bite to it as it will still be cooking in the casserole, try 9 minutes
1cupgrated Parmesanuse the good stuff, NOT the green topped container in the grocery aisle
½cuppanko breadcrumbsor regular is fine or butter crackers crushed up
Instructions
Heat your oven to 400. Grease or butter your best baking dish. Put your pulled rotisserie chicken and cooked pasta in a large bowl.
Melt TWO tablespoons of the butter and a little olive oil (if you want, this keeps the butter from burning) Add the mushrooms and a pinch of salt and sauté over medium-high heat until the all the liquid from the mushrooms evaporates and they get a deep colored caramelization on them, about 15 minutes. Don't move them around a whole lot, but stir a few times while cooking. Add the onion, garlic, thyme, and a little sprinkle of salt, and sauté until the onion is translucent, about 6 minutes. Add the sherry and simmer until it is mostly evaporated, this will take about 2 minutes. Add this mixture to the bowl with the chicken and pasta.
In the same pan, melt the remaining 6 tablespoons of butter and add the flour. Whisk for about 4 minutes until the roux is a bit colored and smells a little nutty, you want to cook the raw flour taste out of it, but you don't want to burn it. Slowly pour in the chicken stock, whisking the entire time until it bubbles and is super thick. Cook this for about 6 minutes. Add the milk, cream, nutmeg and a sprinkle of salt and pepper to the pan and bring to a simmer, you want the mixture to just bubble up, this will take about 10 minutes. Remove from heat and whisk in ½ cup of the parm cheese.
Pour your sauce over the chicken, pasta, mushroom mixture and mix to thoroughly combine. Pour everything into the baking dish, making sure to scrape all that luxurious sauce too.
Mix the remaining ½ cup of parm cheese with the breadcrumbs and sprinkle over the top. Bake for about 25-30 minutes, until the top is golden browned and the entire casserole is bubbly.
Notes
Note: Baking time will be different if made ahead. Bake about 30 additional minutes if made ahead of time and stored in fridge.