Cut 250 g butter into pieces. Put it in a mixing bowl with sugar, 350 g flour and egg. Knead first with the dough hooks of the mixer, then quickly with your hands to a smooth short pastry. Wrap in foil and chill for about 30 minutes.
Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer). Grease a baking tray (35 x 40 cm) and dust thinly with flour. Roll out the dough on it. Bake in a hot oven for 20-25 minutes.
Let it cool down.
Briefly bring 250 g butter, syrup and cream to the boil in a saucepan while stirring. Boil down at medium heat for 20-25 minutes while stirring constantly. Spread on the pastry base and let it cool down completely.
Coarsely chop the chocolate coating and melt in a hot water bath. Leave to cool at lukewarm and then spread on the toffee mixture. Leave to dry. Cut into approx. 3 x 5 cm strips.