Preheat oven to 375°F (190°C)
Roll out the pie crust and fit it into a 9-inch pie dish, prick the bottom with a fork to prevent bubbling
Line the crust with parchment paper and fill with pie weights; bake for 15 minutes to prebake the crust
Remove parchment paper and weights; let the crust cool slightly
In a saucepan, whisk together milk, sugar, cornstarch, egg yolks, and vanilla extract over medium heat
Cook, stirring constantly, until the custard thickens and coats the back of a spoon (about 8-10 minutes)
Remove from heat and strain the custard into a bowl to ensure a silky texture
Peel and slice bananas, arranging them flat in the bottom of the cooled pie crust with a small space between slices
Carefully pour the warm custard over the bananas, allowing it to pool slightly in the spaces
Top with remaining banana slices, placing them vertically around the sides for a decorative finish
If using, sprinkle wheat germ or bread crumbs over the bananas before adding the final custard layer
Return the pie to the oven (lowered to 325°F/160°C) and bake for 45-50 minutes, until the custard is set and golden
Cool completely on a wire rack before refrigerating for at least 2 hours