Method

• 1.
  Put the flours and 1/4 tsp fine salt in a wide mixing bowl. Using fingertips, rub butter into dry ingredients just until butter lumps are the size of whole almonds and flour feels like silky almond meal with buttery lumps throughout. These large butter lumps are going to melt during baking, creating steam, which will flake the pastry apart.
• 2.
  Combine the iced water and egg yolk and then add to the buttery flour. Keep mixing with your hands, lightly squeezing dough together, until it looks like crumbly/shaggy playdough. Wrap dough lightly in plastic, then flatten, by squeezing, into a 2cm-thick round disc with smooth sides.
• 3.
  Chill dough for a minimum of 1 hour or up to 2 days – just ensure the pastry is nicely pliable before rolling.
• 4.
  Roll out half the dough to a 35cm circle, about 3-4mm thick. Trim to a smooth-edged 32cm circle, then gently lift and flop the dough into a 23cm round x 5cm-deep tart pan with a removable base.
• 5.
  Working in sections, tuck dough right into the corner and against the side of the tart pan to prevent air pockets, then use your fingers or rolling pin to push/trim excess dough off the top. Freeze for at least 1 hour before blind baking.
• 6.
  Reserve a little excess dough to patch any cracks after blind baking. With the remaining offcuts, stack and press together. They can be re-rolled twice. Store in the fridge or freezer wrapped in plastic wrap.
• 7.
  To blind bake, preheat oven to 220°C/200°C fan-forced. Cover frozen dough with a piece of aluminium foil (dull side down), tucking it snugly into the corner of the pan. Fill lined pan with 750g caster sugar (see note, opposite). Place in the oven, then reduce the heat to 185°C/165°C fan-forced and bake for 50-60 minutes. Remove foil and bake for another 5-10 minutes so the base crust is a biscuity brown colour.
• 8.
  For the filling, in a medium bowl, add the super-ripe banana, sugar, cornflour, vanilla, gelatine and 1/4 tsp fine salt. Mash to a lumpy paste with a whisk. Add egg yolks and whisk well. Lastly, add the milk and cream. Scrape mix into a 20cm saucepan. The teeny lumps won’t matter. If you want super smooth, whiz the bananas first.
• 9.
  Place the saucepan over medium-high heat and hand whisk with a small balloon whisk at a slow pace to allow the heat to suffuse through the mix. Work the whisk into the corners of the saucepan (where the custard thickens first). After around 3 minutes of whisking, the custard will start to look like a creamy liquid.
• 10.
  Speed up whisking now – the custard will thicken fast. It will look lumpy, but whisk quickly and it will all come together into an evenly thick paste in another 1 minute. As soon as it thickens, slow down the whisking and wait for a few burp-like bubbles to pop over the surface. The custard will look like stiff mashed potato.
• 11.
  Remove pan from heat, scrape custard into a wide bowl and stir in the butter with a stiff plastic spatula until dissolved. Then stir slowly every 5 minutes as it cools to around 25°C so a skin doesn’t form. This will take around 1 hour in a cool kitchen (longer in a warm kitchen).
• 12.
  Grab your blind-baked crust (see notes). Cut the perfectly ripe bananas down the middle lengthways, then into 2cm-wide semi-circles. Gently fold banana pieces into the cooled custard to coat thoroughly. The custard will seal around the banana, staving off oxidisation. If the custard is too hot, this can accelerate browning.
• 13.
  Scrape the mix into the crust, smooth the top and press a piece of plastic wrap to the surface and chill for a minimum of 4 hours or overnight.
• 14.
  For the toffee, set a small heatproof tray lined with baking paper beside the stove and grab a large metal kitchen spoon. Place all ingredients and a pinch of salt flakes in a small saucepan and bring to a fast boil over high heat, stirring to loosen sugar just at the start. The syrup will turn cloudy then start to brown at the edges. Decrease heat to low and cook, constantly stirring, until the caramel crystallises to powdery dust and nuts are an even toasted brown. (It doesn’t matter if the mix crystallises or not. We just want a sugary crunch.) Scrape out onto prepared tray and set aside to cool to room temperature.
• 15.
  To finish, whip the cream with the vanilla. Pile onto the centre of the cooled pie. With an offset spatula, gently push cream to crust edge. Chop the toffee into a chunky dust and scatter over the top.
• 16.
  To serve, saw gently through the cream, clean the knife, then cut through fully along the slice line again to chomp through the filling all the way to the base. If you don’t eat the entire pie once cut, press a piece of plastic wrap against the cut side to delay the banana browning.