I kept having my pastry cream break on me every single service. Turned out I was adding the butter while it was still too hot, about 175 degrees, and I never checked the temp with a probe. Two weeks of wasted batches and angry tickets before a coworker walked by and asked if I was in a hurry. Now I cool it to 140 before emulsifying and it holds perfectly. Anyone else have a basic step that secretly ruined their prep for way too long?