Beat egg yolks and set aside.
Whisk together sugar, flour and salt in a saucepan.
Slowly add milk while whisking. Then add egg yolks while whisking.
Bring to a boil over medium heat while whisking constantly.
Cook until mixture reached the consistency of pudding.
Remove from heat and add vanilla and butter to pan, whisking until butter is melted and mixture is well blended.
Allow to cool completely.
Whip heavy cream until soft peaks form.
Fold whipped cream into custard mixture. and refrigerate until ready to use.
Preheat oven to 400.
Line a baking sheet with parchment paper. Set aside.
Combine butter, water and salt in a medium pan and bring to a boil.
Add flour to the pan and stir until it forms a ball.
Remove from heat and allow to cool for 5 minutes.
Transfer to mixing bowl and beat in the eggs, one at a time.
Transfer pastry dough to piping bag.
Pipe elongated strips of dough onto prepared sheet.
Bake for 40 minutes or until golden.
Remove from the oven and allow to cool completely.
Transfer pastry cream to a piping bag.
Cut pastries halfway through the center with a knife and pipe in the cream.
Melt chocolate by heating chocolate chips and shortening in microwave for 30 seconds, stirring and repeating until melted and smooth.
Place in a shallow flat dish.
Dip tops of eclairs in chocolate and return to parchment lined pan and allow to cool.