01 - Preheat oven to 350°F. Line an 8x8-inch baking pan with parchment paper, allowing overhang for easy removal.
02 - Combine graham cracker crumbs, melted butter, and sugar in a medium bowl. Press mixture evenly into pan bottom. Bake 10 minutes until set. Cool slightly.
03 - Whisk together milk, coconut milk, sugar, cornstarch, and salt in a saucepan. Cook over medium heat, stirring constantly, until slightly thickened (about 3 minutes).
04 - Whisk egg yolks in a separate bowl. Gradually ladle hot milk mixture into yolks while whisking continuously to prevent curdling. Return mixture to saucepan.
05 - Cook over medium heat, whisking constantly, until thick and bubbling (3-5 minutes). Remove from heat. Stir in vanilla and shredded coconut until fully incorporated.
06 - Pour warm filling over cooled crust. Smooth surface with spatula. Refrigerate minimum 1 hour until completely set and firm.
07 - Beat heavy cream, powdered sugar, and vanilla with electric mixer until stiff peaks form. Spread evenly over chilled coconut layer.
08 - Sprinkle toasted coconut flakes over whipped cream. Refrigerate 30 minutes to set. Lift from pan using parchment overhang and slice into 16 bars.