Lightly greased 3 baking trays. Break up the chocolate and gently melt it along with the butter in a bowl set over a pan of simmering water, stirring occasionally.
Take off the heat then stir in the condensed milk until fully incorporated.
Mix in the flour and the chocolate buttons then scoop them onto the tray and refrigerate the cookies for about 10 minutes.
Pre-heat the oven to 180 degrees Fan 160 degrees Gas 4.
Place large teaspoonfuls of the mixture spaced well apart on the prepared baking trays.
Bake in the pre-heated oven for about 15 minutes. The cookies should still look soft and will glisten.
Carefully remove the cookies with a palette knife and cool on a wire rack.