01 - Crush the biscuits into fine crumbs using a food processor or rolling pin. Combine with melted butter until evenly blended.
02 - Press the biscuit mixture firmly into the base of an 8-inch springform pan or individual serving glasses. Chill in the refrigerator while preparing the custard.
03 - Warm the whole milk and heavy cream in a saucepan over medium heat until it just begins to simmer, avoiding boiling.
04 - Whisk together egg yolks, granulated sugar, and cornstarch in a bowl until pale and creamy.
05 - Gradually whisk the hot milk-cream mixture into the egg mixture to temper the eggs, stirring constantly.
06 - Return the combined mixture to the saucepan and cook over low heat, stirring continuously, until thickened and able to coat the back of a spoon, approximately 5 to 7 minutes.
07 - Remove from heat and stir in pure vanilla extract.
08 - Pour the custard evenly over the chilled biscuit base. Cover and refrigerate for a minimum of 2 hours to set.
09 - Top with fresh mixed berries. Optionally dust with powdered sugar and garnish with mint leaves before serving.