- 355g (3 cups) plain flour
- 130g (1/2 cup) granulated sugar
- ½ teaspoon table salt
- 225g (1 cup) unsalted butter, plus 30 g (2 tablespoons), cut into 1/2-inch pieces, or non-hydrogenated margarine (if serving after a meat meal)
- 50g (1/4 cup) dark brown sugar
- 45g (1/2 cup) rolled oats
- 55g (1/2 cup) pecans, chopped
- 240g (3/4 cup) plum jam
- 100g (2 small plums) fresh plums, cut into small pieces
- 1 tablespoon fresh lemon juice from 1 lemon
Adjust oven rack to middle position; heat oven to 180˚C (350˚F). Cover a 13×9 inch baking dish in two lengths of aluminium foil – one going along the length and the other along the width – with enough overhang to be able to use as handles to take the bars out of the pan once cooked. Spray foil-lined pan with non-stick cooking spray.
Using a food processor, process flour, granulated sugar, and salt until combined, about 5 seconds. Scatter 16 tablespoons butter (or margarine) pieces over flour mixture and pulse until mixture resembles damp sand (about twenty 1-second pulses.)
Measure 1¼ cups flour mixture into medium bowl and set aside. Distribute remaining flour mixture evenly in bottom of prepared baking pan. Using hands or flat-bottomed cup, firmly press mixture into even layer to form bottom crust. Bake until the edges begin to brown, 14 – 18 minutes.
While the crust is baking, add brown sugar, oats, and nuts to reserved flour mixture; toss to combine. Work in remaining 30 g (2 tablespoons) of butter or margarine by rubbing mixture between fingers until butter is fully incorporated. Pinch mixture with fingers to create hazelnut-sized clumps; set streusel aside.
Combine jam, plums and lemon juice in small bowl; mash with fork until combined.
Spread filling evenly over the hot crust and sprinkle streusel topping evenly over filling (do not press streusel into filling). Return pan to oven and bake until topping is deep golden brown and filling is bubbling, 22 to 25 minutes. Cool to room temperature on wire rack, 1 to 2 hours; remove from baking pan by lifting foil extensions. Using chef’s knife, cut into squares and serve.