Grease and line a 7inch springform square cake tin with nonstick baking paper. Place the chocolate in a large heatproof bowl and sit over a saucepan of gently simmering water.
Stir until just melted, then remove from the heat and add the lemon juice, extract of lemon and chopped meringue.
Fold gently to mix well then spoon into the lined cake tin.
Chill for 1 hour until set. When ready to serve, turn out from the tin and cut into square portions. Serve stacked in presentation boxes.