Banana Sticky Toffee Pudding 

Preparation

1. Prepare the cake:

   1. Step 1

      Make the banana-date mixture: Select the two ripest bananas, peel them, and break them into pieces. Measure out 1 cup/7 ounces of flesh (a little less is fine, but if you have extra, snack on it or freeze for smoothies or banana bread). Add the bananas to a small saucepan along with the dates, milk and baking soda. (The baking soda helps to break down some of the fibrousness of the dates.) Bring the mixture to a bare simmer over medium heat, mashing with a potato masher to break up the bananas and dates. Reduce the heat to low and continue to cook at a very low simmer, mashing frequently, until you have a thick, coarse paste, about 5 minutes. Remove the saucepan from the heat and set aside to cool.

   2. Step 2

      Arrange an oven rack in the position closest to the broiler heat source and another rack in the center position. Heat the broiler. Brush the bottom and sides of a 9-inch square baking dish with a thin layer of oil. Line the bottom and two opposite sides with a piece of parchment paper, leaving a bit of overhang and smoothing to eliminate most air bubbles. Brush the parchment with a bit of oil and set the baking dish aside. 

   3. Step 3

      Make the banana layer: Place the three remaining bananas on a cutting board and slice off the ends. Halve the unpeeled bananas lengthwise (leaving the peel on will make them easier to arrange later). Place the halves cut sides-up on a small, rimmed baking sheet and sprinkle with 1 tablespoon of dark brown sugar. The sugar is moist, so do your best to distribute it evenly, then rub the sugar into the flesh with your fingertip so it coats the bananas. 

   4. Step 4

      Transfer to the top rack and broil until the sugar is bubbling and the surfaces of the bananas are very well caramelized and even a little charred, 3 to 4 minutes (rotate the pan so they brown evenly and watch carefully to prevent burning). Remove from the oven and set aside to cool slightly. 

   5. Step 5

      Adjust the oven temperature to 300 degrees. Working with one at a time, carefully arrange the banana halves in the bottom of the prepared baking dish, cut sides down, and then remove and discard the peels. Set the pan aside. 

   6. Step 6

      Mix the dry ingredients: In a small bowl, whisk together the flour, baking powder and salt until combined, then set aside. 

   7. Step 7

      Make the batter: In a large bowl, combine the butter and remaining ¾ cup/165 grams dark brown sugar and beat on medium-high with an electric mixer until the mixture is a little pale and a little fluffy, about 2 minutes. Scrape down the sides of the bowl, then add the eggs one at a time, mixing thoroughly between additions. Continue to beat until the mixture is very light and satiny, another 2 minutes. Reduce the mixer speed to low and add a third of the dry ingredients. As the last trace of flour disappears, add about half of the cooled banana-date mixture and mix until combined. With the mixer still on low, add half of the remaining dry ingredients, followed by the remaining banana-date mixture, and then the rest of the dry ingredients. Stop the mixer, then add the walnuts, if using, and, using a flexible spatula, fold the nuts into the batter thoroughly, taking care to scrape the bottom and sides of the bowl, until the nuts are distributed and the batter is evenly mixed. 

   8. Step 8

      Use the spatula to gently dollop the batter across the top of the bananas in the prepared pan, then spread it carefully into an even layer all the way to the sides and corners (the batter is thick, so try your best not to disturb the bananas below). Transfer to the center oven rack and bake until the surface is browned, puffed, and cracked all over, and a cake tester or toothpick inserted into several different places comes out clean, 45 to 55 minutes. 

2. While the cake bakes, make the toffee sauce:

   1. Step 9

      Combine the dark brown sugar, cream, butter and salt in a small saucepan (rinse and reuse the same one from the banana-date mixture). Set the saucepan over medium-high heat and bring to a boil, stirring occasionally with a heatproof spatula to dissolve the sugar. Continue to cook at a boil, stirring occasionally, until the toffee sauce is slightly thickened and reduced, about 2 minutes. Remove from the heat, stir in the vanilla extract, and set aside (you should have about 1 ⅔ cups toffee sauce).

   2. Step 10

      Soak, unmold and serve: When the cake is done baking, remove it from the oven and place on a wire rack. Immediately poke dozens of holes across the surface of the cake with a toothpick, pressing all the way down to the bottom of the baking dish, then pour ⅔ cup of the hot toffee sauce over the surface (reserve the remaining toffee sauce for serving). Let the cake cool until the bottom of the baking dish is warm to the touch but not hot and the sauce is mostly absorbed, 30 minutes to 1 hour. Invert the cake onto a serving platter, then lift off the baking dish and carefully peel away the parchment paper. Cut the cake into squares and serve with the remaining toffee sauce (if necessary, re-warm the sauce over low heat, stirring often).