Step 1: Prepare the Biscuit Base:
Begin by crushing the digestive biscuits (or graham crackers) into fine crumbs. You can use a food processor for this, pulsing until the biscuits are uniformly crushed. Alternatively, place the biscuits in a resealable bag and crush them with a rolling pin until you achieve a fine crumb consistency.
Step 2: Mix the Crust Ingredients:
In a medium-sized bowl, combine the biscuit crumbs with the melted unsalted butter. Mix well until the crumbs are evenly coated with the butter and the mixture resembles wet sand. This step is crucial for ensuring that the crust holds together properly.
Step 3: Press the Crust into the Pie Dish:
Transfer the biscuit mixture to a 9-inch pie dish or tart pan. Use the back of a spoon or your fingers to press the mixture firmly and evenly across the bottom and up the sides of the dish. Ensure that the crust is compact and uniform in thickness to prevent it from crumbling.
Step 4: Chill the Crust:
Place the pie dish in the refrigerator and chill for at least 30 minutes. This allows the butter to solidify, helping the crust to set and maintain its shape. For an even firmer crust, you can chill it for up to an hour.
Step 5: Prepare the Toffee (Dulce de Leche):
There are two methods to prepare the toffee filling. The traditional method involves boiling a can of sweetened condensed milk.
Submerged Can Method: Remove the label from the can of sweetened condensed milk. Place the can in a large pot and cover it completely with water. Ensure the water level remains above the can throughout the cooking process to prevent it from exploding. Bring the water to a gentle simmer, then reduce the heat and continue to simmer for 2-3 hours. The longer it simmers, the thicker and darker the toffee will become.
Once cooked, carefully remove the can from the pot and allow it to cool completely before opening.
Alternate Method:
Pour the sweetened condensed milk into a saucepan and bring to a simmer over medium heat. Reduce the heat to low and cook, stirring constantly, until the mixture thickens and turns a caramel color, about 20-30 minutes. Be careful not to burn the mixture.