Raspberry Crumble Bars

Before you start

These bars use a single oat-and-butter dough twice: most of it is pressed into the pan as a crust and par-baked, and the rest is crumbled on top of a raspberry filling. One dough means one bowl and a base and topping that taste like they belong together.

The filling combines fresh or frozen raspberries with raspberry jam, a little cornstarch and lemon juice. The jam adds body and concentrated flavor, while the berries keep it bright; cornstarch thickens the juices as they bubble so the bars slice instead of oozing. Par-baking the crust is the step that keeps it crisp under all that fruit. Look for the filling bubbling at the edges before you take the pan out; that tells you the starch has thickened.

Ingredients

• Oat dough250 g (2 cups, spooned and leveled) all-purpose flour
• 70 g (¾ cup) old-fashioned rolled oats
• 100 g (½ cup) granulated sugar
• 50 g (¼ cup packed) light brown sugar
• ½ tsp baking powder
• ½ tsp fine salt
• 200 g (¾ cup + 2 tbsp) unsalted butter — melted
• 1 tsp vanilla extract
• Filling300 g (2½ cups) raspberries — fresh, or frozen without thawing
• 160 g (½ cup) raspberry jam
• 1 tbsp cornstarch
• 1 tbsp lemon juice

Method

1. Heat the oven to 175°C (350°F). Line the pan with parchment, leaving an overhang on two sides.
2. Stir together the flour, oats, granulated sugar, brown sugar, baking powder and salt. Add the melted butter and vanilla and mix until the dough forms large, moist clumps.
3. Set aside about 1¼ cups (roughly a third) of the dough for the topping. Press the rest firmly and evenly into the pan.
4. Bake the crust for 15 minutes, until it looks set and dry and the edges are just starting to color.
5. While it bakes, toss the raspberries with the cornstarch in a medium bowl until coated, then gently fold in the jam and lemon juice. Some berries will break; that is fine.
6. Spread the filling over the hot crust, leaving a 1 cm border. Pinch the reserved dough into clumps of various sizes and scatter it over the top.
7. Bake for 30 to 35 minutes more, until the topping is golden brown and the filling is bubbling thickly at the edges and through gaps in the crumble.
8. Cool in the pan on a rack for 2 hours. For the cleanest squares, refrigerate for 30 minutes before lifting out and cutting into 16 bars.

Tips for success

• Squeeze some reserved dough into larger clumps. A mix of big and small pieces gives a more interesting, bakery-style top.
• Frozen berries work well; add them still frozen so they do not bleed, and expect up to 5 more minutes of baking.
• Leaving a small border without filling stops the jam from sticking to the pan and burning.

Substitutions

Raspberries

Blueberries, blackberries or chopped strawberries all work. Strawberries are juicier, so use 1½ tbsp cornstarch.

Rolled oats

Leave them out and add 40 g more flour for a shortbread-style crust and topping without chew.

Raspberry jam

Any complementary jam, such as strawberry or mixed berry, works at the same amount.

Variations

Almond raspberry bars

Add 50 g sliced almonds to the topping and ½ tsp almond extract to the dough.

Lemon raspberry bars

Add 1 tbsp lemon zest to the dough and drizzle the cooled bars with a lemon glaze.

Troubleshooting

The filling is runny when cut

The bars were cut warm or the filling did not bubble long enough to thicken the starch. Bake until it bubbles thickly and cool completely.

Soggy crust

The crust was not par-baked long enough. Bake it until it looks dry and set before adding the fruit.

Topping stayed pale and sandy

It needed more time, or the dough was too dry. Bake until golden and press the topping into clumps rather than scattering loose crumbs.

Storage

Keep covered at room temperature for 1 day, then refrigerate in an airtight container for up to 4 days. The crumble softens a little over time. Freeze cut bars for up to 3 months.

Safety notes

Do not eat the raw dough, which contains raw flour. Contains wheat and milk; oats may be processed with wheat.