Made a roux-base cheese sauce and it didn't work

6 Tbsp butter 1/2 cup flour Made the roux Added 1/2 heavy cream in small batches, It got creamy.

I then added my cheese (1 lb mix of Gouda and Gruyere)

And it broke.

Kinda looks like runny dough soaking in melted butter

It tasted ok, but I couldn't do anything with it. In desperation, i threw in some sour cream to see if it would help. It didn't.

I can usually get it to work, as I do use it over pasta for mac and cheese, so I don't know what I did wrong ghis time. Any ideas?