I made a creamy Cajun chicken pasta last night for dinner. I cooked the cajun chicken in a little bit of butter. Once completely cooked, added the heavy cream and some more seasoning. Let that heat through and thicken up a bit, then added the cooked pasta. Everything as directed in the recipe. I have made this recipe several times and it always does the same thing, as well as similar recipes.

When I make it, it's a creamy sauce. Then the next day when I heat up leftovers, it becomes a buttery sauce. There's no creamyness to it.

Why does my creamy sauce become a butter sauce when I heat up leftovers? Any way to prevent this?