Heat olive oil in a large skillet or wide saucepan over medium-high heat until shimmering.

Add sliced chicken sausage to the hot oil and cook for 4-5 minutes, turning occasionally, until golden brown on both sides.

Add diced onion to the skillet with the sausage and cook for 3-4 minutes until softened and translucent.

Stir in minced garlic and cook for another 30 seconds until fragrant, being careful not to let it burn.

Add the orzo pasta to the skillet, stirring to coat with the oil and combine with the sausage mixture.

Pour in the chicken stock gradually, stirring constantly to prevent the orzo from sticking together.

Bring the mixture to a boil, then reduce heat to medium-low and simmer for 12-15 minutes, stirring frequently, until orzo is tender and most liquid is absorbed.

Stir in the heavy cream and cook for 2-3 minutes until the mixture becomes creamy and thickened.

Add fresh spinach to the skillet, stirring gently until wilted and incorporated throughout the dish.

Remove from heat and stir in grated Parmesan cheese, fresh basil, salt, pepper, and red pepper flakes if using.

Taste and adjust seasoning as needed, then serve immediately while hot and creamy.

Garnish with additional Parmesan cheese and fresh basil if desired before serving.