Line two large baking trays with baking paper.
Sift together the flour, malted milk powder & baking powder.
Using an electric beater or stand mixer, beat the butter and both sugars in a large bowl until pale and fluffy. Add egg and vanilla and continue to beat for another minute or so until fully combined and creamy.
Beat in the flour, one third at a time until just combined. Try not to over mix. Once all the flour is in and the dough is clumping, use your hands to finish bringing the dough together.
Roll small balls of dough (about 2 teaspoons) and sit them on the cookie sheets 1-2 inches apart. Use your thumb to press directly down in the middle to make a large dent in the centre of each.
Place in the fridge for ½ an hour and preheat your oven to 180C / 350F /160C fan forced.
Bake for 10-12 minutes or until golden brown on the edges. Remove from the oven and transfer to a wire rack to cool completely.
Once cookies have cooled, melt the chocolate in the microwave in 30 second increments, stirring between each until fully melted. Fill the indents with chocolate and allow to set before serving.