Heat sugar and water together, boiling until the syrup forms a dark toffee. Remove from heat and quickly stir through muesli. Pour onto a baking tray lined with greaseproof paper and allow to cool. Once cool, smash toffee into fine pieces.
Blend custard powder and apricot jam to a paste with a little of the milk. Place in a saucepan with remaining milk and heat, whisking constantly, until thickened.
Divide pear halves equally into 4 individual ramekins.
Top each with warm custard and finish with a sprinkling of muesli toffee.