Preheat the oven to 400 degrees and set aside a glass casserole dish to bake in. 

Remove the chicken from the bone and shred into bite-sized pieces. Reserve the juices (or jelly if it's still cold) from the bottom of the chicken container. We will add it to the sauce later for extra flavor.

Boil a large pot of water for cooking the spaghetti in. Salt the water well and cover the pot so it boils faster!

Cook spaghetti to al dente, or just a little firmer than usual. Drain and reserve.

Meanwhile, in a skillet or cast iron pan, melt the butter on medium-high heat and add the mushrooms. I like to cut up the rest of the vegetables while the mushrooms brown and caramelize so they have plenty of time to develop a deep, rich flavor. Please be advised that if you use shitakes as I do, that the hard stems must be removed. They are woody and won't cook down. I use a combination of shitakes and button mushrooms!

Add in the small diced yellow bell pepper, poblano, jalapeno, and onion. Stir to incorporate and add 1 t. salt. Cook the vegetables until they begin to soften and wilt at a medium heat, about 4-6 minutes. 

Sprinkle in 2 T flour, and stir into the mixture. Cook 1 minute.

Add in 2 c. chicken stock, and 1 can of Rotel. Stir or whisk well and increase the heat, stirring well, until the mixture begins to thicken. It will thicken as it approaches a simmer. After it has thickened add in the cream.

Add the juice from the rotisserie chicken and 8 oz. of Velveeta. (Cut where the lines are on the package for easy measuring). Turn the heat down to low-medium and allow the Velveeta to melt. This takes 6-8 minutes. Simmer a couple more minutes and taste for seasoning. 

It should taste like heaven at this point and you should have to restrain yourself from pouring it into a bread bowl and calling it soup night. 

In the glass casserole dish, place the drained, spaghetti pasta and the shredded chicken, and give it a toss around. Pour the sauce over the top. Give it another toss and sprinkle it with cheddar cheese.

Cook at 400 degrees for about 10-15 minutes, just to get it nice and bubbly and allow the cheese topping to melt. Garnish with cilantro if desired.