I put a video on youtube, pastry cream in 7 minutes.
Notice I do the whole process on FULL flame, no simmering. it should be cooked and off the stove in 60 seconds.
I was fighting with the camera which slowed me down a little bit.
Don't cook it like creme anglais, low flame and a slower cooking process only increases the chance of scorching.
But I suspect the problem is how you're handling it after its made.
Authentic french eclairs are filled with choc pastry cream, just add semi sweet choc (not cheap chips) whilst its still in the saucepan and mix til its melted, about 10 seconds.
Coffee eclairs just get coffee extract. Or just leave it plain, suptoyou.
Pour out, cover and chill.
Beat it in the mixer with a paddle until smooth, then add rum or whatever you like to use.
If thats not smooth enough to your liking you can beat it over a bowl of ice cubes until cool.
1 qt milk
2 eggs
4 oz sugar
5 oz AP flour.
Salt and vanilla if you want,
I can't eat salt and vanilla is too exp for me.