Preheat oven to 190 degrees C. Line a 20x30cm baking pan with foil and grease it well. Line the pan with crispbread squares.
In a medium saucepan, melt the butter. Add the brown sugar and cook, stirring it until it dissolves. Bring to a boil and cook about 3 minutes, stirring constantly. Immediately pour mixture over the crispbread.
Bake for 3 to 5 minutes or until the mixture starts to bubble. Spread the chocolate chips over the top. Let set for a minute. Spread the chocolate evenly when melted. Sprinkle with nuts. Let cool, then cut into bars.