Cook the orzo: Bring a large pot of salted water to a boil. Add orzo and cook according to package directions until just al dente, about 8 minutes. Drain thoroughly and set aside.
Season and cook chicken: Pat chicken breasts dry and season with onion powder, garlic powder, paprika, salt, and pepper. Heat olive oil in a large skillet over medium-high heat. Cook chicken 5 minutes per side until golden and cooked through to 165°F. Rest 5 minutes, then dice into chunks.
Saute vegetables: In a large skillet or Dutch oven, melt butter with olive oil over medium-high heat. Add onion, carrots, and celery. Saute for 5 minutes until softened with glossy edges.
Make the roux: Reduce heat to medium-low. Sprinkle flour evenly over vegetables. Stir constantly for 2-3 minutes until a thick paste forms.
Create cream sauce: Slowly pour in chicken broth while whisking continuously. Add heavy cream and whisk until smooth. Stir in chicken bouillon powder. Simmer gently for 3 minutes until sauce thickens and coats a spoon.
Combine everything: Fold in diced chicken and cooked orzo. Stir gently but thoroughly until everything is coated in cream sauce. Heat through for 2-3 minutes, stirring occasionally. Add more broth if too thick. Taste and adjust seasoning.
Serve: Spoon into bowls and garnish with fresh parsley if desired. Serve immediately while hot and creamy.