Grease square springform pan (24 x 24 cm; alternatively round, 26 cm Ø). Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer). Cut chocolate bars into slices approx. 1⁄2 cm thick.
Place the cookies in a large freezer bag, seal it and roll a pastry roll over it until the cookies crumble finely.
Knead cookie crumbs and 75 g butter. Pour into the mould and press to a base. Spread condensed milk on top. Spread chocolate bars and chocolate drops on top.
Bake in a hot oven for about 20 minutes. Remove from the oven and leave to cool in the mould. Remove the cake from the tin and cut into approx. 30 rectangles (each approx. 2 x 7 cm).