Method

• 1.
  Preheat oven to 170°C/150°C fan-forced. Grease base and sides of a 22cm x 9.5cm, 10cm-high loaf pan and line with baking paper.
• 2.
  Place the flour, 1 cup (220g) caster sugar and baking powder in a large bowl and whisk to combine. Add the remaining ingredients to a large jug and whisk until smooth. Pour into the flour mixture and stir until just combined.
• 3.
  Pour into the prepared pan and bake for 55 minutes, or until a skewer inserted in centre of loaf comes out clean. Cool loaf in pan for 10 minutes, then transfer to a wire rack to cool completely. Wash loaf pan.
• 4.
  Level the loaf with a serrated knife, cutting away the slightly domed top (enjoy the cut-off pieces of cake while working on your loaf). Fold a 30cm sheet of foil lengthways into 3 to strengthen, and place across base of loaf pan, with foil extending over edges of pan (this will help you to lift cake out of pan). Return cake, cut-side up, to pan.
• 5.
  To make custard, place milk and vanilla in a medium saucepan over medium heat and bring almost to the boil. Whisk yolks and sugar in a large heatproof bowl until pale. Add cornflour and whisk until combined. Slowly whisk in one-third of the milk mixture until smooth, then whisk in the remaining milk mixture. Pour into a cleaned medium saucepan and cook, whisking constantly, over medium heat for 5 minutes, or until mixture comes to the boil and becomes very thick. Pass through a fine sieve into a large bowl and whisk in the rum, if using, until perfectly smooth. Pour over the cake and level with a spatula. Chill, uncovered, for at least 2 hours to firm up.
• 6.
  Using foil, lift loaf from pan and transfer to a serving plate. Sprinkle top with extra caster sugar and and use a blowtorch to caramelise the top (you want a dark caramel so it’s not overly sweet, and contrasts with the custard). Chill for at least 15 minutes for caramel to set and custard to cool (see recipe notes).
• 7.
  Serve cut into slices.