Heat & thin: In a medium pot, warm the spaghetti sauce and stir in the broth. Start with 1 cup, then add more until it’s a soup-like consistency.
Simmer: Bring to a gentle simmer over medium heat and let it bubble for about 10 minutes so the flavors deepen.
Creamy finish: Reduce heat to low. Stir in the cream and butter. Don’t let it boil once the dairy is added — just warm gently.
Balance & season: Taste and add a pinch of sugar if it’s too tangy. Season with salt, pepper, and herbs if you like.
Blend (optional): For an ultra-smooth texture, use an immersion blender right in the pot.