MAKE THE SHORTCRUST PASTRY:
1. Combine the flour, powdered sugar, and salt in a large bowl. Whisk briefly to blend.
2. Add the frozen cubes of vegan butter. Using your fingertips or a pastry cutter, rub the butter into the flour until the mixture resembles coarse breadcrumbs with some pea-sized pieces remaining. Work quickly — cold butter is essential for a flaky, light crust.
3. Drizzle in the ice-cold water, 1 tablespoon at a time, mixing gently with a butter knife after each addition. Stop adding water as soon as the dough just begins to hold together when pressed. It will look crumbly — that is correct.
4. Turn the mixture onto a lightly floured surface and press it together into a flat disc. Do not knead. Wrap tightly in cling film and refrigerate for at least 30 minutes (up to 24 hours).

BLIND-BAKE THE TART SHELL:
5. Preheat the oven to 180°C / 350°F (fan 160°C / 325°F). Place a baking sheet on the middle rack to preheat.
6. On a lightly floured surface, roll the pastry out to approximately 3mm (⅛-inch) thickness. Carefully drape it over a 23cm (9-inch) fluted tart tin with a removable bottom. Press gently into the corners without stretching. Trim excess pastry by rolling a rolling pin over the top edge.
7. Prick the base lightly with a fork. Line with parchment paper and fill with baking beans or dried rice.
8. Blind-bake for 15 minutes. Remove the parchment and beans, then bake for a further 8–10 minutes until the base is light golden and feels dry to the touch. Set aside. Reduce oven temperature to 165°C / 325°F (fan 150°C / 300°F).

PREPARE THE RICE PUDDING FILLING:
9. Bring the water to a boil in a medium saucepan. Add the Arborio rice and a pinch of salt. Cook at a gentle boil for 8–10 minutes, stirring occasionally, until the rice is par-cooked and still noticeably al dente — it should have a distinct bite at the center. Drain any remaining water.
10. Return the rice to the pan over low heat. Add the coconut milk, oat milk, sugar, vanilla, and lemon zest. Stir to combine.
11. Cook gently, stirring frequently, for 12–15 minutes. The rice should absorb most of the liquid and become creamy but retain a pleasant al dente texture. The mixture should be thick enough to hold its shape on a spoon but still flow slowly. It will firm up further as it bakes and cools.
12. Pour the rice pudding into the blind-baked tart shell and spread evenly with the back of a spoon. Allow to cool for 10 minutes while you prepare the biscotto topping.

MAKE THE FRANGIPANE BISCOTTO TOPPING:
13. In a bowl, combine the almond flour, all-purpose flour, sugar, baking powder, lemon zest, and salt. Whisk to blend.
14. Add the oil, oat milk, and almond extract. Stir with a fork until a crumbly, slightly cohesive dough forms. It should resemble damp sand that holds together when pressed.
15. Using your fingers, crumble the biscotto mixture evenly over the top of the rice pudding filling in an irregular layer. Some areas should be thicker, some thinner — this creates textural contrast where the frangipane bakes into a dry, biscuit-like crust.

BAKE THE TART:
16. Place the tart on the preheated baking sheet. Bake at 165°C / 325°F for 25–30 minutes, until the frangipane topping is golden brown and feels firm and dry to the touch — it should have the texture of a crisp biscuit, not a soft cake.
17. Remove from the oven and cool completely in the tin on a wire rack. The tart must be fully cool before unmolding and garnishing.

MAKE THE CANDIED LEMON ZEST:
18. Using a sharp vegetable peeler or channel knife, cut long thin strips of zest from the lemons, avoiding the white pith. Slice into fine julienne strips.
19. Bring a small saucepan of water to a boil. Blanch the zest strips for 2 minutes, then drain. Repeat this blanching process two more times with fresh water each time. This triple blanching removes bitterness while preserving the sharp citrus punch.
20. In the same saucepan, combine the sugar and water. Bring to a simmer, stirring until the sugar dissolves.
21. Add the blanched zest strips. Simmer gently over low heat for 15–20 minutes until the strips become translucent and the syrup thickens.
22. Using a fork, transfer the candied strips to parchment paper, separating them so they do not clump. Allow to cool and dry. They should be glossy, slightly tacky, and intensely lemony.

MAKE THE CARAMELIZED ALMOND FLAKES:
23. Place the flaked almonds in a dry skillet over medium heat. Toast, stirring frequently, until golden and fragrant, about 3–4 minutes.
24. Sprinkle the sugar over the almonds. Continue stirring as the sugar melts and coats the almonds in a thin golden caramel, about 2–3 minutes more. Watch carefully — the transition from golden to burnt happens quickly.
25. Immediately pour the caramelized almonds onto parchment paper. Sprinkle with a pinch of flaky salt. Allow to cool completely, then break apart any clusters.

MAKE THE LEMON GEL:
26. In a small saucepan, combine the water and agar agar powder. Whisk thoroughly — the agar must be fully incorporated before heating.
27. Bring to a gentle boil over medium heat, stirring frequently. Once boiling, reduce heat and simmer for 1–2 minutes until the agar is completely dissolved.
28. Remove from heat. Stir in the sugar until dissolved, then add the lemon juice. Adding the lemon juice after removing from heat preserves its brightness and prevents the acid from weakening the agar's setting power.
29. Pour into a shallow dish or small container. Allow to set at room temperature for 20–30 minutes, then refrigerate until firm, about 1 hour.
30. Once set, use a fork or small whisk to break the gel into a smooth, spoonable consistency — it should be glossy and slightly wobbly, like a loose jam.

ASSEMBLE AND SERVE:
31. Carefully unmold the cooled tart from its tin and place on a serving board or plate.
32. Arrange the candied lemon zest strips artfully across the top of the biscotto crust.
33. Scatter the caramelized almond flakes over and around the candied zest.
34. Serve slices with a generous spoonful of lemon gel on the side or dolloped on the plate. The gel's sharp acidity is essential — it cuts through the richness of the coconut rice pudding and the sweetness of the tart.