In a medium saucepan, whisk gelatin and milk together. Bring to a simmer over medium heat until gelatin is dissolved. In a small bowl whisk, egg yolks, half-and-half, sugar, and cornstarch until smooth. Whisk a small amount of hot milk mixture into egg and repeat a total of three times. Return all to saucepan and bring to a simmer over medium heat, whisking occasionally until pudding is smooth and thickened.

Remove from heat and immediately whisk chocolate chips, cocoa, and vanilla into pudding until chocolate is melted. Allow pudding to cool slightly, then transfer to a medium bowl, press plastic wrap directly on surface, and let chill in refrigerator 1 hour.

Remove chilled pudding from refrigerator and beat on medium speed with a handheld electric mixer until smooth. Fold 1 cup whipped cream into pudding until just combined.

Scrape filling into pre-baked pie crust and gently smooth top. Cover pie with plastic wrap and let chill in refrigerator at least 2 hours. Just before serving, spread or pipe remaining whipped cream on top of pie. Garnish with berries if desired. Slice pie and enjoy!