Prepare ingredients: remove sausage from casings if necessary and crumble, drain and chop sun-dried tomatoes, grate Parmesan, chop onion, and mince garlic so all components are ready to use.

Heat a large heavy-bottomed pot over medium-high heat and add the olive oil; when shimmering, add the sausage and cook, breaking it up until well browned and most fat is rendered, about 6–8 minutes.

Push the browned sausage to one side, add the butter to the empty space, then add the chopped onion and a pinch of salt; cook until the onion is translucent and shows light browning about 4–5 minutes before stirring together.

Add the minced garlic, tomato paste, dried oregano, and crushed red pepper flakes if using; cook, stirring constantly, for 30–60 seconds until the tomato paste darkens slightly and the garlic is fragrant.

Pour in the white wine to deglaze the pot, scraping up browned bits from the bottom; allow the wine to reduce by roughly half, 1–2 minutes.

Stir in the chopped sun-dried tomatoes and chicken stock, bring to a gentle simmer, reduce heat to medium-low, and simmer for 8–10 minutes to meld flavors.

Add the heavy cream and half of the grated Parmesan; taste and season with salt and freshly ground black pepper, adjusting consistency with up to 1/2 cup water if necessary; warm gently for 2–3 minutes without boiling vigorously.

Add the gnocchi directly to the simmering soup and cook until they float and are tender, usually 2–4 minutes, stirring gently to prevent sticking.

Fold in the baby spinach a handful at a time until wilted but still bright green, about 1–2 minutes, then remove the pot from heat and stir in the remaining grated Parmesan to melt into the broth.

Ladle the soup into bowls, finish with an extra grating of Parmesan and freshly ground black pepper to taste, and serve with crusty bread for dunking if desired.