Begin by crushing the digestive biscuits into fine crumbs using a food processor or by placing them in a zip-top bag and rolling with a rolling pin. Melt the unsalted butter in a saucepan or microwave, then combine it with the biscuit crumbs. Press this mixture firmly into the bottom of a 9-inch tart pan to form an even layer, and refrigerate for 1 hour until set.

In a heavy-bottomed saucepan, add the sweetened condensed milk and cook over medium heat for 5-7 minutes, stirring constantly until it thickens and turns a golden color. Pour the warm toffee mixture over the chilled biscuit base, spreading it evenly, and allow it to cool to room temperature.

Once the toffee has set completely, slice fresh bananas into thin rounds and layer them evenly over the toffee to balance the sweetness.

Take a chilled mixing bowl and add the heavy cream, powdered sugar, and vanilla extract. Using an electric mixer, beat the mixture on medium-high speed until you achieve soft peaks, which should take around 3-4 minutes. Spread the whipped cream generously over the banana layer.

For an optional decorative flair, melt some dark chocolate and drizzle it over the whipped cream, or create chocolate shavings. After decorating, refrigerate the pie for at least 2 hours.