Preheat the oven to 175°C 345°F/Gas 3–4. Place the apricot halves in a single layer in the base of a high-sided baking dish. Combine 200 ml (7 fl oz) of water, the sugar, Lillet Blanc, half the lemon zest and the pineapple sage in a saucepan. Bring just to a simmer and cook for 5 minutes to combine the flavours and dissolve the sugar. Turn off the heat and allow to infuse for 10 minutes. Return to a simmer, then immediately pour over the apricots. Let the apricots cool completely in the liquid.
To make the custard, spread the reserved apricot stones on a baking tray and bake for 10 minutes. Allow to cool, then crack each stone in half with a nutcracker or meat mallet. Remove the kernels and discard the stone carcass. Combine the apricot kernels with the milk, cream, honey, corn, vanilla bean, remaining lemon zest and a tiny pinch of salt in a saucepan over medium heat and bring to a simmer for 2 minutes. Remove from the heat, cover and allow the flavour to infuse for 10 minutes. Strain and reserve. In a large bowl, whisk the eggs until smooth, then slowly add the strained milk mixture until combined. Pour into a 20 cm (8 inch) square baking dish, so the liquid comes roughly 2.5 cm (1 inch) up the sides. Bake, uncovered, for 45–60 minutes or until completely set and the centre barely trembles. The objective is to cook through rather than having a slightly runny centre as you might with a crème brûlée. Allow the custard to cool to room temperature, then pour into a blender and blend until smooth. Cover and refrigerate to cool.
To make the corn cake, grease and line a 20 cm (8 inch) round cake tin. Beat the butter and sugar in bowl of an electric mixer until light and fluffy. Add the honey, lemon zest and vanilla seeds and beat until smooth. Add the egg and beat until smooth.
Sift the dry ingredients into a bowl and stir to combine. Add half of the flour mix to the cake batter, alternating with the buttermilk, until all the ingredients are just combined. Gently fold in the corn kernels and pour the batter into the prepared cake tin, spreading it out evenly. Bake for 20 minutes or until a skewer inserted in the centre comes out clean, the top is lightly golden, and the sides begin to pull away from tin. Allow to cool in the tin on a wire rack, then remove from the tin and cut into four wedges.
To make the salted almond toffee, grease a small baking sheet with olive oil and spread the toasted almonds in a single layer. In a small saucepan over low heat, combine the sugar, brown sugar, salt and butter, stirring until completely dissolved. Increase the heat until the mixture becomes light caramel in colour and measures 150°C (300°F) on a sugar thermometer. Immediately remove from the heat, stir in the bicarbonate of soda, and pour over the toasted almonds. Allow to cool, then break into pieces. Put the broken pieces in a food processor and pulse in short bursts until the toffee forms soft crumbs.
When ready to serve dessert, heat a frying pan over medium–high heat. Butter all sides of the corn cake wedges and toast in the frying pan until golden on all sides. Spoon the custard into shallow bowls. Top with toasted corn cake and poached apricots. Sprinkle with almond toffee crumbs and thinly sliced sage leaves.