The snaps do both, they should be added at the very end when the cooking is complete. If you can, check your snaps first. I made some a couple of months ago & used Nabisco snaps. Yecchh!
They have really sweetened their snaps, I guess to appeal to a wider market but they really loused up my braten. There is another brand out there, the name evades me at present but it is in a brown bag type package, they are more like the old fashioned snaps.