Muffins can be made up to three days ahead. Keep in an airtight container. For a change, try replacing blueberries with raspberries and walnuts with almonds.
340g packet classic sultana cake mix
3/4 cup buttermilk
50g unsalted butter, melted
2 eggs, lightly beaten
125g punnet blueberries
½ cup walnuts, finely chopped
¼ cup firmly packed brown sugar
1 tablespoon plain flour
½ teaspoon ground cinnamon
25g unsalted butter, chopped
Line a 6-hole Texas muffin pan (3/4-cup capacity) with paper muffin wraps.
To make streusel, combine walnuts, sugar, flour and cinnamon in a small bowl. Add butter. Rub in with your fingertips until well combined.
Place cake mix in a large bowl. Make a well in centre. Add buttermilk, butter and eggs. Stir with a wooden spoon until just combined. Gently stir in blueberries.
Spoon mixture evenly into muffin wraps. Sprinkle evenly with streusal.
Cook in a moderate oven (180C) for about 25 to 30 minutes, or until just firm in centre when lightly touched. Remove from oven. Stand in pan for 5 minutes. Transfer to a wire rack to cool.
Serve muffins warm or at room temperature.