Streusel Alsacien

Ingredients

• For the yeast base
• 500 g plain flour
• 7 g dried yeast
• 250 ml whole milk, warmed to 24°C
• 2 eggs
• 100 g unsalted butter, softened
• 60 g caster sugar
• 1 tsp vanilla extract
• 5 g fine salt
• For the streusel
• 250 g plain flour
• 250 g caster sugar
• 200 g unsalted butter, cold, 8–10°C, cut into small cubes
• For the optional middle layer
• 300 g crème pâtissière or quark, traditional in the Ribeauvillé style; omit for the Strasbourg plain version
• To finish
• 30 g icing sugar, for dusting while still warm

Method

1. 1
   Combine the flour, sugar, salt, and yeast for the base in a large bowl. Add the warmed milk, eggs, and vanilla; mix to a shaggy dough. Work in the softened butter in stages, kneading until the dough is smooth, supple, and pulls cleanly from the bowl. Cover and proof at 24°C for approximately 90 minutes. The dough is ready when it has exactly doubled in volume and a finger pressed in leaves an impression that springs back slowly.
2. 2
   While the dough proofs, make the streusel. Combine the flour and sugar in a cold bowl. Add the cold butter cubes and work with fingertips only — never a machine — pressing and snapping the butter into the dry ingredients until irregular clumps form, ranging from pea-sized to walnut-sized. Stop before the mixture becomes uniform: heterogeneity is the measure of success. Transfer to a tray and freeze for 15 minutes. The streusel is ready when it holds its shape when lightly pressed but fractures apart at the least force.
3. 3
   Butter the rectangular mould thoroughly. Press the proofed dough evenly into it without deflating it entirely — some residual air is desirable. If using the Ribeauvillé variation, spread the crème pâtissière or quark in an even layer over the dough at this point. Scatter the streusel from the freezer thickly across the entire surface, to a depth of at least 2 cm, without pressing it down. This is where the dish lives or dies: an insufficient layer produces a cake that is merely bread with a dusting; a full, generous, uncompacted scatter produces the shattering crunch that defines the Streusel Alsacien.
4. 4
   Bake at 175°C for 25 to 30 minutes. At the correct moment, the streusel will be a deep, even golden brown — not pale, not dark amber — and the base, tested with a skewer inserted at the centre, will come out clean. The kitchen will smell of browned butter and vanilla; a raw or muted butter scent signals the cake needs more time.
5. 5
   Remove from the oven and dust immediately with icing sugar while the surface is still warm, so the sugar adheres lightly and does not disappear into the crumble. Allow to cool in the mould for 10 minutes before cutting. At the correct texture, the first cut will cause the streusel to shatter and cascade; the base beneath will be soft and yielding. Both contrasts must be present.