Heat the oven to 185C (165 fan)/360F/gas 4¼.

Pour the oil into a casserole dish that will comfortably accommodate the lamb shanks, and put it on a medium-high heat.

Season the shanks, brown them all over in the hot oil, then transfer to a plate.

Add the chopped celery, onion, chopped garlic and oregano to the pot, and sweat, stirring, on a gentle heat for about five minutes, until soft.

Reintroduce the lamb shanks to the pot meatiest side down, then sprinkle over the tinned tomatoes and wine.

Cover the pot (or baking dish) with a lid or foil, then bake for an hour and a quarter.

Flip over the shanks, so they now sit meatiest side up, then pour in the orzo and stir and shake the pot so the pasta falls into the cooking liquid.

Return the pot to the oven, this time uncovered, for another half and hour, by which time the shanks should be tender and the orzo cooked.

Taste the liquor and adjust the seasoning as necessary.

While the pasta is cooking, make the gremolata. Finely grate the lemon zest and the remaining garlic clove on to a board.

Put the parsley leaves on top of the grated lemon and garlic, then finely chop so they end up all mixed together.

Sprinkle the gremolata over the lamb and serve at once.

For the pastry, put both flours in a food processor with the sugar, salt and half the butter, then blend to the consistency of breadcrumbs.

Add the remaining butter and blend again, until the second batch of butter is broken down to the size of hazelnuts.

Tip the mix into a large bowl, add three-quarters of the ice-cold water and mix quickly and thoroughly until everything comes together into a dough.

Shape into a disc, wrap in clingfilm and rest in the fridge for at least half an hour.

Meanwhile, make the frangipane. In a food processor or stand mixer, beat the butter and sugar until pale and creamy.

Stir in one of the eggs until well combined, then work in the ground almonds.

Roll out the rested pastry into a roughly 26cm-diameter disc that’s about the thickness of £1 coin, and lay it on an unlined baking sheet.

Spread the frangipane over the top of the pastry, leaving a 2½cm border all around the edge.

Arrange the rhubarb neatly on top of the frangipane layer, trimming as necessary.

Lift the pastry border up and over the rhubarb at the sides.

Whisk the remaining egg to make an egg wash, then brush this all over the exposed pastry.

Sprinkle the demerara sugar over the egg-washed pastry, then put the tart in the fridge for 10-15 minutes.

Meanwhile, heat the oven to 170C (150C fan)/340F/gas 3½.

Bake the tart for an hour, but check on the rhubarb after 40 minutes.

Remove the tart from the oven, leave to cool for at least 20 minutes, then slice and serve with creme fraiche or whipped cream.