Preheat the oven to 350°F (175°C). Grease a 9-inch pie pan.
Combine the crushed chocolate cookies and melted butter in a bowl until the crumbs are evenly moistened. Press the mixture firmly into the bottom and up the sides of the prepared pie pan to form the crust.
Bake the crust for 8 minutes, then remove from the oven and let cool slightly while you prepare the filling.
Place the chopped chocolate and heavy cream in a heatproof bowl. Microwave in 30-second intervals, stirring between each, until the chocolate is melted and smooth. Alternatively, heat the cream and pour over chocolate, letting it sit for 2 minutes before stirring.
Whisk in the granulated sugar, a pinch of salt, the beaten eggs, and vanilla until fully combined and glossy.
Pour the chocolate filling into the prepared crust and smooth the top. Bake for 30 to 35 minutes, or until the center is set but still slightly jiggly.
Allow the pie to cool on a wire rack for at least 1 hour before serving. Serve warm or at room temperature, optionally with vanilla ice cream or whipped cream.
Notes
For a deeper fudge flavor, use bittersweet chocolate. To serve, warm slices briefly in the microwave and top with ice cream.