How to Fix Runny Boston Cream Filling
Things You'll Need
Instructions
1Chill the runny cream pie filling. The filling needs to be cold to set up properly, and chilling it for several hours in the fridge will help you determine how much additional thickening it needs.
2
Sift into your filling bowl one tablespoon cornstarch for every cup of filling liquid. Whisk the cornstarch in thoroughly, until the filling is smooth and no starchy lumps or streaks remain.
3
Scrape the filling into your saucepan and heat over medium heat, stirring constantly to avoid scorching.
4
Bring the filling to a slow bowl, so that three to five large bubbles pop on the top of the filling. Your filling will have started thickening now.
5
Reduce the heat to low and simmer, without stirring, for 30 to 45 seconds, or until the filling is thick and glossy.
6
Scrape the filling into a clean bowl. Do not stir the filling after this point. Place a clean piece of plastic wrap directly on top of the filling and chill the filling in the fridge for several hours, or until very thick.
Source...