Tarte à la Rhubarbe

an Alsatian rhubarb custard tart: tender rhubarb pieces baked in a rich crème fraîche and egg custard within a short, buttery pastry shell, the definitive French expression of a dessert that the Alsace has made its own

Origin: England — the Kitchen Gardens of Georgian Britain

From the journey of Rhubarb.

Rhubarb came to the kitchens of Alsace through the same channel that brought it to much of Northern and Central Europe: the kitchen garden tradition of the Rhine valley borderlands, which drew freely on both French and German horticultural practice. Alsace, positioned at the cultural and geographic crossroads between the French and German worlds (and politically part of one or the other at various points in its history), developed its own rhubarb tradition that is at once distinctly French in technique and thoroughly regional in character: the crème fraîche custard tart, filled with rhubarb and baked in a thin, short pastry shell, is a preparation that belongs nowhere else so completely as it belongs to the Alsatian table. The custard in an Alsatian tarte à la rhubarbe is not the English-style egg custard that might be poured over a rhubarb pudding; it is the appareil of the region's great quiche tradition, made with crème fraîche or cream, eggs, and a modest amount of sugar, set just firmly enough to hold but still trembling slightly at the centre when the tart comes from the oven. The rhubarb pieces are arranged in the raw pastry shell, the custard poured over, and the whole baked together until the pastry is crisp, the rhubarb is tender, and the custard has set around and between the pieces. Some Alsatian cooks macerate the rhubarb in sugar for an hour before adding it to draw out excess moisture and prevent a watery custard; others arrange the pieces raw and trust the short cooking time to prevent this. The result is a dessert of elegant simplicity: sharp, creamy, and sweet in shifting proportion with each forkful.

Ingredients

Pastry

200 g plain flour
100 g cold unsalted butter, cut into small cubes
2 tbsp icing sugar
1 egg yolk
2 tbsp cold water
1 pinch fine salt

Filling

500 g rhubarb stalks, cut into 3 cm pieces
80 g caster sugar (for the rhubarb)

Custard

200 ml crème fraîche (full-fat)
2 large eggs
60 g caster sugar (for the custard)
1 tsp vanilla extract
1 tbsp plain flour (to thicken the custard slightly)

Method

Macerate the rhubarb: toss the rhubarb pieces with 80 g caster sugar in a bowl. Leave at room temperature for 30–60 minutes. Drain off the juice that collects (discard or reduce for another use) and pat the pieces dry with kitchen paper. This removes excess moisture that would otherwise make the custard watery.
Make the pastry: in a large bowl, rub the cold butter into the flour and icing sugar until the mixture resembles coarse breadcrumbs. Stir in the salt. Mix the egg yolk with the cold water, add to the bowl, and mix with a palette knife until the dough just comes together. Do not overwork. Form into a disc, wrap, and refrigerate for 30 minutes.
Preheat the oven to 190°C (170°C fan). Roll the pastry out on a lightly floured surface to about 3 mm thickness. Line a 24 cm tart tin with a removable base. Trim the edges, prick the base with a fork, line with baking paper and baking beans, and blind-bake for 15 minutes. Remove the beans and paper and bake for a further 5 minutes until the base is just pale gold. Remove from the oven and reduce the temperature to 170°C (150°C fan).
Make the custard: whisk together the crème fraîche, eggs, caster sugar, vanilla extract, and flour in a jug until smooth.
Arrange the drained rhubarb pieces in a single layer in the pastry shell, packing them reasonably snugly. Pour the custard mixture over the rhubarb; it should come almost to the top of the pastry case. Bake at 170°C for 25–30 minutes until the custard is set around the edges but still has a very slight tremor at the centre when the tart is gently shaken.
Leave to cool in the tin for at least 30 minutes before unmoulding. Serve warm or at room temperature, dusted lightly with icing sugar. Crème fraîche or lightly whipped cream alongside is traditional.

Notes

The flour in the custard is the Alsatian insurance against a custard that splits or weeps; some bakers omit it for a purer, silkier texture, relying instead on accurate temperature control. A small pinch of ground cardamom in the custard adds a faint, aromatic warmth that flatters both the cream and the rhubarb. Leftover tart can be refrigerated for 2 days; the pastry will soften slightly but the flavour improves.

The Gastrographer

Name: Tarte à la Rhubarbe
Prep time: 30 min
Cook time: 45 min
Total time: 1 h 15 min
Yield: 6
Cuisine: England — the Kitchen Gardens of Georgian Britain
Ingredients: 200 g plain flour; 100 g cold unsalted butter, cut into small cubes; 2 tbsp icing sugar; 1 egg yolk; 2 tbsp cold water; 1 pinch fine salt; 500 g rhubarb stalks, cut into 3 cm pieces; 80 g caster sugar (for the rhubarb); 200 ml crème fraîche (full-fat); 2 large eggs; 60 g caster sugar (for the custard); 1 tsp vanilla extract; 1 tbsp plain flour (to thicken the custard slightly)

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Journey Point Map Key

Ingredient originTrade or transit route

Became a culinary stapleColonial / trade control