In this delicious twist on the favourite Cinnamon oatmeal raisin cookie, an oatmeal cookie crust is layered with a tangy buttermilk custard, sweet rum raisin sauce and a crunchy oat crumble. A drizzle of icing sugar and buttermilk glaze completes the classic pairing of milk and cookies.
Pre-heat the oven to 220°C, 425°F, Gas Mark 7.
For the rum raisin sauce place raisins and rum into a blender, cover and blend on high speed until smooth then pass through a sieve into medium saucepan. Cook on medium heat for 10-12 minutes, or until thickened stirring frequently. Set aside.
Place 50g (2oz) of the oats in food processor. Pulse to coarsely chop, add flour, sugar and 1 tsp of the Cinnamon, pulse to mix well. Add the cold butter and pulse until mixture resembles coarse crumbs. Add 2 tbs of the buttermilk and pulse to mix well. Reserve 2 tbs of the oat mixture in small bowl, then press remaining oat mixture into bottom of 20cm (8 inch) square greased foil-lined baking pan. Mix reserved oat mixture and remaining oats and spread onto a small baking sheet.
Bake crust and oat crumble together in the oven for 8-12 minutes, or until golden brown. Remove crust and oat crumble from oven and reduce oven temperature to 170°F, 325°C, Gas Mark 3. Set aside the oat crumble for serving, then pour Rum Raisin Sauce into prepared crust.
Meanwhile, mix sugar and melted butter in large bowl with wire whisk until well blended. Add eggs, mix well. Stir in the remaining buttermilk, (reserving 2 tbs for icing) the remaining ½ tsp Cinnamon and the seeds from the Vanilla Pod. Pour over sauce in crust.
Bake for 45-50 minutes, or until custard is set and just golden brown around the edges. Cool completely on wire rack.
Just before serving, mix icing sugar and remaining 2 tbs buttermilk, until smooth. Sprinkle top of cooled dessert with oat crumble then drizzle with glaze. Cut into bars to serve.