Heat a large pot over medium-high heat and add the Italian sausage, breaking it into bite-sized pieces with a wooden spoon as it cooks. Brown the meat for 7-10 minutes until it develops a deep golden color and is cooked through—this creates rich, savory flavor that forms the foundation of the soup. Remove the cooked sausage with a slotted spoon, leaving about 1 tablespoon of fat in the pot to cook the aromatics.

In the same pot with the sausage fat, add the diced onion and celery, cooking for 4-5 minutes until softened and fragrant. Sprinkle the flour over the vegetables and stir constantly for about 1 minute to toast it lightly, then add the minced garlic and cook for another 30 seconds until aromatic. This flour coating (called a roux) will thicken the soup and create a silky texture once the liquid is added.

Gradually pour in the chicken broth while stirring constantly to dissolve the flour and prevent lumps from forming. Add the cooked sausage back to the pot along with the diced tomatoes and Italian seasoning, then bring everything to a gentle boil. I like to taste the broth at this point and season lightly with salt and pepper—this ensures the flavors develop evenly throughout the soup.

Add the refrigerated cheese tortellini directly to the simmering soup and cook for about 5 minutes, stirring occasionally to prevent sticking. Refrigerated tortellini cooks much faster than dried varieties and maintains a better tender texture, so don't be tempted to cook them longer or they'll become mushy.

Pour in the heavy cream and stir gently to combine, then simmer for about 5 minutes to let the cream warm through and meld with the broth. Add the fresh spinach and stir until it wilts completely, which takes just 1-2 minutes. Taste the soup and adjust seasoning with additional salt and pepper as needed before serving—the cream will have mellowed some of the spice, so you may need a bit more seasoning at the end.