Preheat the oven to 180°C.
Blitz up digestive biscuit until fine consistency. Then add to a bowl with melted unsalted butter. Mix well & firmly press down in a lined square baking tray. Bake for 15-20 minutes. Cool for 5 minutes.
Over low to medium heat, combine the sweetened condensed milk and unsalted butter (100g) in a saucepan, whisking continuously for 5 minutes. When bubbles begin to appear, whisk for an additional minute, then remove from heat.
Pour caramel over the base.
Bake for 15-17 minutes and cool for 30 minutes at room temperature (if you have time), then place in fridge.
Microwave the chocolate in 20-second intervals and then stir in oil.
Pour chocolate evenly over the caramel layer.
Refrigerate for ~2-3 hours or until set.
