In a large mixing bowl cut together with a pastry cutter ( or use 2 knifes ) the flour , powdered milk , baking powder , 1/2 cup of the brown sugar and the butter , cut until crumbly.
Add coconut ; Beat the egg yolks and stir in crumb mixture.
Pack the mixture into a buttered 9" square pan.
Beat the egg whites until stiff but not to stiff ; Gradually add the remaining 1 cup brown sugar ; continue beating until glossy , about 3 minutes ; Spread over top coconut crumb mixture ; Swirl with knife to make interesting pattern.
Bake @ 325° for 20-25 minutes until meringue is firm and lightly browned.
Cool in the pan and then cut into square bars.
If they last that long , store in an air tight container.