Crush the Oreo cookies finely in a food processor or by placing in a sealed bag and rolling with a rolling pin.

In a bowl, mix the Oreo crumbs with the hot fudge topping and melted butter until uniform. Set aside.

Sprinkle the gelatin over the strong coffee in a small bowl and let sit for 1 minute. Gently heat until the gelatin dissolves fully. Remove from heat.

Stir the melted bittersweet chocolate into the coffee–gelatin mixture until smooth. Let cool slightly.

In a separate mixing bowl, beat the cream cheese and sugar together until smooth. Add sour cream and the coffee‑chocolate mixture; beat again until creamy.

Fold in whipped cream gently, retaining lightness. Chill mousse.

In small dessert glasses or cups, layer Oreo mixture, then mocha mousse, repeating until cups are filled.

Garnish each with a swirl of whipped cream and top with an espresso bean or Oreo half, if desired. Chill until ready to serve.