Mix the chocolate crumbs and melted butter and press them firmly into a 9-inch pie plate; freeze for 15 minutes.
Beat the cream cheese, condensed milk and cocoa until smooth.
Dissolve the espresso in the hot water and beat it into the cream-cheese mixture with the vanilla and salt.
Beat the heavy cream to medium peaks and fold it into the mocha mixture, then fold in the mini chocolate chips.
Spread the filling in the crust and freeze for at least 8 hours, then stand each slice at room temperature for 10 minutes before serving.