Start by heating the olive oil in a large pan over medium heat. Once hot, add the diced onion and sauté until translucent, about 3–4 minutes. Then add minced garlic and cook for an additional minute until fragrant.
Next, stir in the chopped sun-dried tomatoes and let them cook with the onion and garlic for another minute.
Pour in the broth and bring everything to a gentle simmer. Allow it to cook for about 5 minutes. After that, add in the heavy cream gradually while stirring continuously until well combined.
Gently fold the butter beans into your creamy sauce along with grated Parmesan cheese. Stir everything together carefully. Season with Italian seasoning, salt, pepper, and red pepper flakes if using.
Allow your mixture to simmer on low heat for about another five minutes until everything is heated through and creamy. Just before serving, stir in chopped fresh basil leaves.