Preheat the oven to 160C (325F). Line an 8 x 8 inch (20 x 20 cm) baking pan with aluminum foil and set aside.
Put the flour, baking soda, baking powder and salt in a large bowl and mix with a fork. Stir in the brown sugar, walnuts, pecans and dried fruit. Mix with your hands making sure that the fruit and nuts are coated with the flour mixture.
In a separate bowl, beat the egg and the vanilla with a whisk or stick blender until pale and thick. Add the egg mixture to the fruit and nut mixture and mix until all the fruit and nut pieces are coated with the batter. Spread into the prepared pan, pressing to even it out.
Bake for about 35 to 40 minutes, or until the batter is golden brown and has pulled away from the sides of the pan. Cool the bars on a wire rack and use a sharp knife to cut into squares.