Whisk together marinade ingredients (2 tbsp olive oil, 1 tbsp lemon juice, 1 tbsp Worcestershire, 1/2 tbsp Dijon, 1/2 tsp salt, 1/4 tsp pepper) in a large freezer bag or bowl; add chicken, toss to coat, and refrigerate 30 minutes to 4 hours.
Bring a large pot of salted water to a boil and cook tortellini al dente according to package directions; reserve 1 cup pasta water, then drain and set aside.
Preheat oven to 400°F. 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 baguette and toss to coat. Spread in a single layer on a baking sheet and bake about 10 minutes or until golden to make croutons.
Heat 1 tbsp olive oil in a large skillet over medium-high. Remove chicken from marinade, pat dry, and add to skillet. Cook undisturbed 3–5 minutes until browned, flip, cover and reduce heat to medium; cook 5–7 minutes more until cooked through. Transfer to a cutting board and rest 5 minutes, then chop or slice.
In the same large skillet melt 1 tbsp butter with 2 tbsp olive oil over medium. Add minced garlic and sauté about 30 seconds until fragrant.
Sprinkle in 3 tbsp flour and cook, stirring, about 2 minutes to form a roux.
Turn heat to low and slowly whisk in 2 cups milk until smooth, then 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 (parsley, basil, onion powder, 1/2 tsp salt, oregano, pepper, red pepper flakes).
Increase heat to medium-high and simmer, stirring constantly, until sauce slightly thickens. Reduce heat to low and stir in cream cheese until melted, then stir in 1/2 cup grated Parmesan until smooth.
Add drained tortellini and chopped chicken to the sauce and toss to coat; add reserved pasta water a little at a time if needed to reach desired consistency. Taste and adjust salt, pepper or lemon juice as needed.
Serve topped with freshly grated Parmesan, croutons and chopped fresh parsley.