Preheat oven to 180 C / Gas 4. Grease an 20cm round cake tin and line the bottom with a circle of greaseproof paper.
Mix digestive biscuit crumbs, melted butter, 3/4 teaspoon banana flavouring and 3 tablespoons sugar in a bowl until mixture holds together; transfer into bottom of prepared cake tin and press down firmly.
Bake in the preheated oven until base is lightly browned, about 8 minutes. Set aside to cool.
Melt peanut butter chips with single cream in a bowl set over a pan of boiling water. Stir until the chips have melted and the mixture is smooth; set aside to cool.
Place cream cheese into the mixing bowl of a stand mixer and slowly mix, using paddle attachment, until cream cheese is smooth. Increase speed to medium and beat in 100g caster sugar. Beat eggs into mixture, 1 at a time, blending the next egg in after the previous one is fully incorporated. Beat in bananas, vanilla extract, 1/2 teaspoon banana flavouring and lemon juice, stopping occasionally to scrape the sides of the bowl. Finally, beat in melted peanut butter chip mixture until smooth and even. Pour filling on top of the biscuit base.
Set the cheesecake into a large, deep roasting tin. Pour enough water into the tin to reach most of the way up the sides of the cake tin, creating a water bath. Bake cheesecake in the preheated oven until filling is set, about 1 hour. Turn off oven, open door and let cheesecake cool slowly in the oven for 1 hour.
Run a knife around the inside of the cake tin and flip the tin over onto a cooling rack. Place a dish towel on the bottom of the tin. Use a hot kettle to rub the dish towel, gently heating the bottom of the cheesecake; slowly remove tin. Place a serving plate on top and use the wire rack to flip the cake back over onto the plate. Refrigerate cheesecake for 8 hours.
Peanut butter chips:
You can find Reeses® peanut butter chips in larger supermarkets in the baking aisle.