Whisk sugar, cornstarch, and salt in a saucepan; gradually incorporate milk and egg yolks until homogenous.

Cook over medium heat while stirring continuously with a whisk until the custard thickens and reaches a light boil.

Remove from heat, stir in vanilla extract, and pass through a fine-mesh sieve into a clean bowl to ensure a smooth texture.

Press plastic wrap directly onto the surface of the custard and refrigerate for 4 hours or until completely chilled.

Beat heavy whipping cream and powdered sugar in a chilled bowl until stiff peaks form.

In a large glass trifle bowl or individual dishes, layer Biscoff cookies followed by sliced bananas.

Spread a portion of the chilled custard over the bananas and drizzle with 2 tablespoons of melted Biscoff spread.

Repeat the layering process until all components are utilized, finishing with a layer of whipped cream.

Garnish with crushed Biscoff cookies and a final drizzle of Biscoff spread before serving.