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1
Preheat the oven to 400u00b0F. Line a baking sheet with parchment paper and lay the rhubarb stalks on top. Sprinkle over 1/4 cup of sugar and bake for 15-20 mins, until slightly softened. Leave to cool on the baking sheet.
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2
For the streusel mix, stir together 2 1/3 cups flour, brown sugar, ginger, cinnamon, lemon zest and a pinch of salt in a bowl. Pour in the melted butter, knead together and crumble with fingertips.
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3
Stir the quark or mascarpone, milk, oil, 1/4 cup sugar, vanilla extract and a pinch of salt in a bowl. Mix in the remaining flour and baking powder and knead to a smooth dough. On a lightly floured surface, roll this dough to a 9 x 13 inch rectangle.
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4
Grease a 9 x 13 jelly roll pan. Line with parchment paper, overhanging paper by 2 inches on short sides. Grease parchment paper and dust with flour. Place the rolled out dough in the pan. Spread over the jam. Layer one third of the streusel mix and the rhubarb (lengthways) on top, then sprinkle over the remaining streusel mix. Bake for about 30 mins.
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5
Leave to cool in the pan, then carefully remove. Cut in half lengthwise, then cut each length into 6-7 pieces. Serve dusted with powdered sugar and whipped cream, if desired.
