When the powdered milk has melted and a fine, thick, uniform mass has been obtained, pour half the mass into a bowl with white and half the mass into a bowl with dark chocolate. Combine the chocolate with the milk powder mixture by mixing. When the masses are uniform they are ready to be poured into a mold. Pour the mixture with white chocolate on the bottom of the mold, which is previously covered with a transparent adhesive foil, and then arrange the roasted hazelnuts. Pour the remaining mixture of white chocolate over the hazelnuts, and the mixture of dark chocolate over it.