Preheat the oven to 350 degrees F. Butter and line a 9-by-9-by-2-inch baking pan with parchment paper, allowing a 2-inch overhang. Butter the lining too.
Whisk together the flour, baking powder and salt in a medium bowl and set aside.
Melt the butter in a medium saucepan; add both sugars and whisk until combined and the sugar is melted, about 5 minutes. Transfer the mixture to a medium bowl and let cool slightly. Whisk in the eggs and vanilla extract until combined. Add the flour mixture and whisk until just incorporated. Fold in the chocolate chips, almonds and toffee chips and transfer the mixture to the prepared pan.
Bake until the top cracks slightly and is firm to the touch and a skewer inserted into the center comes out with moist pieces clinging to it, 24 to 27 minutes. Remove to a wire rack and let cool completely. Remove the bars from the pan using the parchment handles, transfer to a cutting board and cut into 2-inch squares.