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• Macerate both, drain, reduce. As with peach pie, and even more so here. Rhubarb is 93% water.
• Cut the rhubarb thick — 2 cm. Thin slices dissolve completely and the filling becomes a purée. Thick pieces keep some shape.
• Do not use the leaves. Rhubarb leaves carry oxalic acid at toxic levels; only the stalk is food. See Rhubarb.
• Tapioca handles acid better than cornstarch in a filling this sharp.
• More sugar than feels right. 250 g for a kilo of fruit. Rhubarb absorbs sweetness without ever tasting sweet.
• A lattice, so the very wet filling can reduce.

One 23 cm pie. Serves 8.

• 1 batch all-butter pie crust
• 600 g rhubarb, cut in 2 cm pieces
• 500 g strawberries, hulled and halved
• 250 g granulated sugar
• 40 g tapioca starch, or 35 g cornstarch
• 4 g fine salt
• zest of 1 orange
• 1 tsp vanilla — see Pure vanilla extract
• 20 g unsalted butter
• 1 egg beaten with 1 tbsp milk
• coarse sugar

Toss the rhubarb and strawberries with the sugar, salt and zest. Leave one hour — it will pool badly.

Drain into a pan and reduce the liquid to about 80 ml. Cool, then return it to the fruit with the starch and vanilla.

Line the tin and chill; cut lattice strips.

Heat the oven to 220 °C / 425 °F with a heavy tray inside.

Fill, dot with butter, lattice, chill 20 minutes, glaze and sugar.

Bake 20 minutes at 220 °C, then 190 °C / 375 °F for 45–55 minutes, until bubbling thickly in the centre.

Cool at least four hours.

• Forced rhubarb, grown in the dark, is pink, tender and much milder; field rhubarb is green, sour and better in a pie.
• Rhubarb freezes perfectly. Cut, spread on a tray, freeze, bag — and use it frozen with 15 minutes added.
• Keeps two days at room temperature. The crust softens fast under this filling.

Method and theory: Pie and tart recipes · pies and tarts · Rhubarb · Strawberries

Nearby: blueberry pie · peach pie · fruit galette