Heat the olive oil in a large pot over medium heat.
Add the Italian sausage, breaking it up with a spoon as it cooks.
Stir in the diced onion and cook until translucent, about 3–4 minutes.
Add the minced garlic and cook for an additional minute until fragrant.
Pour in the chicken broth and bring the mixture to a simmer.
Add the tortellini to the pot and cook according to package instructions, usually about 3–5 minutes.
Stir in the heavy cream and mix well, letting it heat through.
Add the chopped spinach and Italian seasoning, stirring until the spinach wilts.
Taste and adjust seasoning with salt and pepper before serving.