Custard pie won't set
I've tried twice to make the buttered rum cream pie in the Four & Twenty Blackbirds Pie Book, and both times the (delicious) filling has failed to set. I've followed the recipe exactly and have made other successful custard pies and puddings before, so I'm feeling pretty confident about my custard-making chops and wondering if the recipe is the problem. Has anyone successfully made this pie, or do you have advice about how to make it sturdier? As far as thickening ingredients go, the filling contains 6 Tbsp butter, 1/2 cup heavy cream, 3 Tbsp cornstarch, 2 1/2 cups whole milk, and 4 large egg yolks.