Blackberry-Apple Oat Crumble Bars

Jammy blackberry pockets and tender apple slices are tucked into a buttery oat crumble, baked into sturdy bars that stay delicious for lunchboxes.

Ingredients

• 2 medium apples (about 450g / 1 lb), peeled (optional), cored, thinly sliced
• 2 cups blackberries (about 300g / 10–11 oz), fresh or frozen
• 2 tbsp lemon juice (or apple cider vinegar in a pinch)
• 1/3 cup sugar (white or brown), plus 1 tbsp extra if your fruit is very tart
• 2 tbsp cornstarch (cornflour)
• 1 tsp vanilla extract
• 1 1/2 cups rolled oats
• 1 1/2 cups all-purpose flour
• 1/2 cup brown sugar, packed
• 1/2 tsp ground cinnamon
• 1/2 tsp fine salt
• 3/4 cup unsalted butter, melted (or neutral oil, see Tips)

Method

• 1

  Step 1: Prep the pan

  Heat oven to **180°C / 350°F (160°C fan)**. Line a **20cm / 8-inch square** baking pan with baking paper, leaving overhang so you can lift the bars out later.

• 2

  Step 2: Make the jammy fruit filling

  In a bowl, gently toss **apples, blackberries, lemon juice, 1/3 cup sugar, cornstarch, and vanilla** until the cornstarch disappears and the fruit looks glossy. Let sit while you make the crumble (this helps the apples start releasing juices).

• 3

  Step 3: Mix the oat crumble

  In a large bowl, mix **oats, flour, brown sugar, cinnamon, and salt**. Pour in the **melted butter** and stir until you get a damp, clumpy mixture. When you squeeze some in your hand it should hold together in soft clumps (not dry and dusty).

• 4

  Step 4: Press the base

  Tip about **two-thirds** of the crumble into the lined pan. Press down firmly (use the bottom of a measuring cup) into an even layer—this is what makes lunchbox-sturdy bars.

• 5

  Step 5: Add filling + top crumble

  Spread the fruit mixture evenly over the base, including all juices. Scatter the remaining crumble over the top, squeezing some into bigger clumps for a gorgeous craggy topping.

• 6

  Step 6: Bake

  Bake for **35–40 minutes**, until the top is **golden brown** and you can see **bubbling purple juices** at the edges.

• 7

  Step 7: Cool completely (important!)

  Cool in the pan for **at least 2 hours** (or refrigerate 45–60 minutes) until fully set. Lift out using the paper overhang, then slice into **12 bars** with a sharp knife (wipe the blade between cuts for clean edges).

Tips

• **Frozen blackberries work отлично** — Don’t thaw; toss straight in with the apples. Add an extra **1 tsp cornstarch** if your berries are very icy/watery.
• **Sweeter or tarter fruit** — Taste a blackberry and a slice of apple. If tart, add the optional **1 tbsp sugar**; if very sweet, reduce sugar by **1–2 tbsp**.
• **Make them extra lunchbox-proof** — Chill overnight before slicing. They’ll be firmer, less crumbly, and easier to pack.
• **Butter substitute** — You can use **1/2 cup neutral oil** instead of butter for a softer, more cookie-like bar (still sturdy once chilled).
• **Storage** — Keep in an airtight container **3 days at room temp** or **up to 6 days in the fridge**. Freeze (wrapped) up to **2 months**; thaw overnight in the fridge.
• **Serving ideas** — Perfect as-is for lunchboxes; at home, warm a bar and serve with **yogurt, whipped cream, or vanilla ice cream**.

Nutrition (per serving, estimate)