01 -  In a mixing bowl, combine chicken chunks with plain yogurt, tikka masala paste, lemon juice, and salt. Marinate for 15 to 30 minutes. Heat oil in a skillet over medium-high heat, add the marinated chicken, and cook until fully cooked through and slightly charred. Set aside. 
 02 -  Bring a large pot of salted water to a boil. Add fusilli and cook until al dente according to package instructions. Drain and set aside. 
 03 -  In the same skillet, melt butter over medium heat. Pour in heavy cream and pesto, whisking to combine. Stir in grated Parmesan, if using. Season with salt and black pepper. 
 04 -  Add the drained fusilli and cooked chicken tikka to the sauce. Toss well to coat evenly and heat through for 2 to 3 minutes. 
 05 -  Serve pasta hot, topped with fresh basil or cilantro and chili flakes if desired.