For a stronger Milo taste, add more Milo powder. I highly suggest to lessen the amount of flour in proportion to the additional Milo powder added if it's quite substantial. Texture of final product changes when the dough is too dry (ie cookie looses the melt in mouth effect and just becomes bite size crumble cookies). If you find the dough too soft to handle, the butter may have softened too much/melted in the sweltering tropical heat. Try chilling the dough for an hour before rolling it.