Method

1. Grease and line a 20cm/8in square tin with baking parchment and grease again. Preheat the oven to 180C/350F/Gas 4.

2. First make the sticky topping. Place the butter and soft light brown sugar in a small pan over a medium heat. Once the butter is melted, turn up the heat and let the mixture bubble away for a few minutes, until it begins to thicken slightly. Stir it frequently so it does not catch on the bottom.

3. Pour the mixture into the bottom of the lined tin and tip the tin back and forth to spread it out evenly. The mixture will eventually solidify in the tin so make sure to spread it out now.

4. Next, tip the pecans (if using) onto a baking tray and toast in the oven for five minutes. Set aside to cool.

5. Now make the sponge mixture. Cream together the butter and sugar in a large bowl (or food mixer) until light and fluffy. Add the eggs one at time, beating hard between each addition. Split the vanilla pod open, scrape the seeds out into the mixture (or add the vanilla extract). Then fold in both flours, the baking powder, ginger, cinnamon, treacle and salt and set aside.

6. Slice the bananas into 5mm/¼in thick pieces. Arrange them in a single layer in the bottom of the tin. I line them up so they are nice and straight but of course it is fine to do them in any old order too. Pack them all in tight so they don’t move around once the cake mix goes over. Then drizzle over the calvados (if using).

7. Roughly chop the pecans and stir them through the cake mix. Now, carefully dollop the cake mix over the bananas and gently spread it out with the back of a spoon or palate knife, levelling the top. Pop it into the oven for about 45 minutes.

8. After 35 minutes, remove the cake from the oven and insert a metal skewer or the blade of a small knife right into the centre (but not touching the bottom. It should come out completely clean. If there is some cakey gooeyness left on it just pop it back in the oven for another five minutes or so.

9. Once the cake is cooked remove it from the oven and leave to cool in the tin for about 10 minutes. Then put a large flat plate over the top of the tin and holding the tin and the plate, flip the whole lot over so that the tin is now upside down. Gently remove the tin and carefully peel off the baking parchment.

10. Cut into squares and serve warm or cold with your choice of crème anglaise, softly whipped cream or ice cream.