Make the caramel
Caramel seems to be unbuyable at present, but the method of boiling for 3 1/2 hours was a little too much effort. So we tries using the oven instead, which worked very well.
Preheat the oven to 220C.
Pour the condensed milk into a glass pie plate or shallow baking dish (I used a tall souffle one).
Set the dish in a roasting pan and add hot water until it comes halfway up the side of the dish.
Cover the dish tightly with foil and bake for 1 to 1 1/4 hours. Check during baking and add more water if needed.
Remove and leave to cool.
Whisk until smooth.

Make the biscuit base
1 packet hobnobs (350g)
150g butter

Melt the butter and add the crushed biscuits.
Press into a flan dish and refrigerate.

Spread caramel over the biscuit base.
Slice the bananas and spread over the caramel.
Whip the cream, adding 1 tsp crushed instant coffee. Spread over the bananas.
Sprinkled with a little more powdered coffee.

Make the mini-pies in the same way in silicone muffin cases or ramekins.

Addendum
Variations from 2 years ago, to avoid their being lost.
Banoffee Cake
I made 2 sandwich sponge cakes and sliced each in half horizontally. I then prepared some whipped cream with coffee and layered toffee, bananas, and cream on each slice. Mmm.

Banoffee-fudge cupcakes
I also made sponge cupcakes, with the addition of small chopped up chunks of fudge. I think another time I’ll try flouring them before mixing them into the batter, or use a butter-based cake recipe, as they sank to the bottom of my cupcake liners (and melted and tasted delicious). I then topped each cupcake with toffee, a slice of banana and piped on a swirl of coffee-whipped cream.
Decadence in a bite!

And my comment from back then bears repeating:
Of course the nicest part is that you can just put your spoon into the tin of toffee and eat up a spoonful – all by itself!