Start by combining instant coffee, sugar, and 1–2 tablespoons of milk in a mixing bowl. Whisk on high speed until the mixture turns creamy, pale, and thick.
Pour in the liquid whipping cream and continue whipping until the mixture forms soft peaks.
Next, add the condensed milk and whip for another 2 to 4 minutes, until the mixture becomes light and fluffy.
If you’d like to add some crunch, drizzle melted chocolate over the top. Let it sit for about 5 minutes to firm up, then give it a final whip to break up the chocolate into little crispy bits throughout the ice cream.
Line your pan with parchment paper, making sure to leave extra hanging over the sides so you can lift it out easily once frozen.
Separate the bourbon biscuits by twisting them apart, and arrange the halves with the cream side facing up across the bottom of the pan to form a base layer.
Spread the whipped ice cream evenly over the biscuit layer, smoothing it out with a spatula. Then top with the remaining biscuit halves, placing them cream-side down and cookie-side facing up.
Freeze the assembled sandwiches overnight until fully set. Once frozen, slice into bars and serve straight from the freezer.