Preheat oven to 350°F. Line an 8x8-inch pan with parchment paper leaving a 2-inch overhang at each side.
Whisk together melted butter, both sugars, almond butter, vanilla, salt and egg until smooth. Whisk in baking powder. Stir in flour. Fold in the chocolate chunks.
Spread the dough out into your prepared pan and press it evenly into the base. Bake for 18-20 minutes until the top is golden, edges are browned and it still feels slightly soft in the middle. Transfer pan to a wire rack and let cool completely.
For the topping, melt together milk chocolate, almond butter and oil in a small saucepan over very low heat or in the microwave until smooth and spread it over the cooled bars. Dollop teaspoons of almond butter over top and swirl it through. Refrigerate for 1 hour until set before slicing.