Mix the sugars and butter in a large bowl using an electric hand mixer to blend them together until the mixture looks smooth and creamy.
Crack each egg into the mixture, mixing well between each egg and pausing to scrape down the sides with a spatula. Mix in the vanilla.
Sift in the flour and baking powder, then mix well with a wooden spoon.
Stir in the chocolate chunks. Use your hands to squeeze the dough together in 1 big lump, then split into 2 even pieces. Put each piece on a sheet of cling film.
Roll each piece of dough in the cling film so that they form thick sausage shapes, then seal the ends. Put them in the fridge and chill for at least 3 hrs or overnight
Heat oven to 180C/160C fan/ gas 4. Take the dough rolls out of the fridge, unwrap and use a small knife to slice each one into 12 pieces, so you have 24 in total.
Place the slices on a baking tray lined with baking parchment and bake for 20 mins or until the cookies are golden brown on the edges, but still pale in the centre.
Allow to cool slightly before lifting them onto a wire rack to cool completely. Sandwich the cookies together with ice cream and dig in!