Whisk 2 tbsp olive oil, 1 tbsp lemon juice, 1 tbsp Worcestershire, 1/2 tbsp Dijon, 1/2 tsp salt and 1/4 tsp pepper in a large freezer bag or bowl. Add the chicken, toss to coat, then refrigerate 30 minutes to 4 hours.
Bring a large pot of salted water to a boil and cook the tortellini until al dente per package directions; reserve 1 cup pasta water, then drain and set aside.
Preheat oven to 400°F (200°C). In a medium bowl whisk 3 tbsp olive oil, 2 tbsp finely grated Parmesan, 1/4 tsp garlic powder and 1/8 tsp salt. Add cubed bread and toss to coat, spread on a baking sheet and bake about 10 minutes or until golden.
Heat 1 tbsp olive oil in a large skillet over medium-high. Remove chicken from marinade, pat dry, and sear undisturbed 3–5 minutes until browned. Flip, cover, reduce heat to medium and cook 5–7 minutes more until cooked through. Transfer to a cutting board and let rest 5 minutes, then chop or slice.
In the same large skillet, melt 1 tbsp butter with 2 tbsp olive oil over medium heat. Add minced garlic and sauté ~30 seconds. Sprinkle in 3 tbsp flour and cook, stirring, about 2 minutes to form a roux.
Reduce heat to low and slowly whisk in 2 cups milk. Add 1 1/2 tbsp lemon juice, 1/2 tbsp Dijon, 1 tsp Worcestershire, 1 tsp fish sauce, 2 tsp chicken bouillon and the dried seasonings (1/2 tsp each parsley, basil, onion powder, salt; 1/4 tsp each oregano and pepper; 1/4 tsp red pepper flakes).
Increase heat to medium-high and simmer, stirring constantly, until sauce slightly thickens. Reduce to low and stir in the 2 oz softened cream cheese until smooth, then add 1/2 cup grated Parmesan and stir until melted.
Add cooked tortellini and chopped chicken to the sauce and toss to coat, adding reserved pasta water a little at a time to reach desired consistency. Adjust salt, pepper and lemon juice to taste.
Serve topped with freshly grated Parmesan, the baked croutons and chopped fresh parsley if desired.
