Before starting, preheat the broiler to high. Wash and dry all produce. Add 10 cups warm water and 2 tsp salt (use same for 4 ppl) to a large pot. Cover and bring to a boil over high heat. While water comes to a boil, roughly chop spinach.

Pat chicken dry with paper towels, then season with half the Montreal Steak Spice (use all for 4 ppl). Heat a large oven-proof pan over medium-high heat. When hot, add 1 tbsp oil (dbl for 4 ppl), then chicken. Pan-fry until golden-brown, 1-2 min per side. Transfer chicken to a foil-lined baking sheet. Broil in the middle of the oven until chicken is cooked through, 5-6 min.** Carefully wipe the pan clean.

While chicken broils, add fusilli to the boiling water. Cook uncovered, stirring occasionally, until tender, 10-12 min. Reserve 1/4 cup pasta water (dbl for 4 ppl), then drain and return fusilli to the same pot, off heat.

Reheat the same pan (from step 2) over medium. When hot, add 2 tbsp butter (dbl for 4 ppl), then onions, garlic puree and spinach. Cook, stirring often, until spinach wilts, 2-3 min. Add cream cheese and cream. Cook, stirring often, until cream cheese melts, 1-2 min.

Add fusilli and reserved pasta water to the pan with sauce. Season with salt and pepper, then stir to combine. Remove the pan from heat. (NOTE: If you do not have an oven-proof pan, transfer mixture to a lightly oiled 8x8-inch baking dish here; for 4 ppl, use a 9x13-inch baking dish.) Sprinkle with cheese. Broil in the top of the oven until cheese melts, 4-5 min. (TIP: Keep an eye on cheese so that it doesn't burn!)

Divide chicken and pasta between plates. Sprinkle chili flakes over pasta, if desired.