Preheat oven to 325°F.
In a mixing bowl, beat the softened butter until creamy. Add the sugar and vanilla, beating until light and fluffy.
Scrape down the sides of the bowl, and add the egg, beating well.
Add the chopped nuts, apricot pieces, and white chocolate chips, mixing until incorporated.
Sift in the flour and baking powder. Add the salt and mix until stiff and well-combined. If the mixture seems too dry, add the milk, one tablespoon at a time, until a thick batter is achieved.
Transfer the mixture to a square baking pan that has been sprayed with non-stick spray and lined with parchment paper. Spread evenly.
Bake for 25-30 minutes until lighten golden brown in color and a toothpick inserted into the center comes out with just a few moist crumbs. The center should still be soft.
Cool in pan for a few minutes before removing to cool completely on a wire rack.
Cut into 9 large bars or 18 smaller.
Store for several days in an airtight container.