Crush caramel biscuits into fine crumbs. Combine with melted unsalted butter and press into the bottom of a springform pan. Refrigerate for 10 minutes.

Blend softened cream cheese with caster sugar until smooth. Soak gelatin sheets in cold water, then dissolve in hot milk. Stir in Earl Grey tea powder and combine with cream cheese.

Whip the whipping cream to soft peaks and gently fold into the cream cheese mixture along with the crushed caramel biscuits.

Pour the cheese mousse over the biscuit base, smooth the top, and refrigerate for at least 4 hours or overnight.

For the optional mirror glaze, steep an Earl Grey tea bag in hot milk, dissolve caster sugar, and add pre-soaked gelatin. Cool to room temperature.

Pour the cooled mirror glaze over the set mousse and refrigerate for an additional 1-2 hours.

Unmold the cheesecake, decorate with crushed caramel biscuits, slice, and serve chilled.