Preheat your oven to 400°F and bake the chicken tenders according to package directions, usually 15-20 minutes, until golden and crispy. While they cook, finely dice the celery and slice the green onions (green parts only), setting them aside for garnish. Once the chicken is done, let it cool slightly, then chop it into bite-sized pieces. Set aside 1/2 cup of chopped chicken for garnish and reserve the rest for mixing into the sauce.
In a large pot, melt the butter over medium heat. Once melted and foaming, add the flour and stir constantly for 30 seconds to cook out the raw flour taste—this creates your roux. Pour in the water slowly while stirring to avoid lumps, then continue stirring until the mixture thickens into a smooth base. Add the milk gradually, stirring well to combine. This creates a silky foundation for the cheese sauce.
Add the dry pasta, salt, ranch powder, and paprika to the sauce base and stir well to combine and separate the pasta strands. Bring the mixture to a gentle simmer over medium heat, stirring occasionally to prevent sticking and ensure even cooking. Cook for 10-12 minutes, stirring every couple of minutes, until the pasta is tender and has absorbed much of the liquid. I like cooking the pasta directly in the sauce rather than separately—it saves dishes and lets the pasta absorb all those ranch and spice flavors from the start.
Reduce the heat to low and add the shredded cheddar cheese, Monterey Jack cheese, cream cheese, and buffalo wing sauce to the cooked pasta mixture. Stir constantly for 2-3 minutes until all the cheeses are melted and the sauce is smooth and creamy. If the sauce seems too thick, add a splash of milk to reach your desired consistency. The cream cheese adds richness, while the buffalo sauce gives it a subtle tangy kick.
Stir the bulk of the chopped chicken from Step 1 into the cheesy pasta mixture until evenly distributed. Transfer to a serving dish or bowl, then drizzle the additional 2 tablespoons of buffalo sauce over the top for extra flavor and visual appeal. Top with the reserved 1/2 cup of chopped chicken, the diced celery, and sliced green onions. Serve immediately while hot and creamy.