Chocolate topped crunchy slice

Ingredients
Mars bars 4 (65 gm each) chopped
Butter 90 gm
Rice crispy cereal 3 cups
Ingredients for topping
Milk chocolate 200 gm chopped
Butter 30 gm
Method
Grease a 19*29 cm lamington pan, in a sauce pan combined mars bars and butter, stir continuously over low heat without boiling until mixture is smooth, stir in rice crispy cereal, mix well and press mixture evenly into prepared pan, spread with topping, refrigerate until set before cutting.
Method for topping
Melt chocolate and butter in a pan over hot water stir until smooth.