Place the butter, chocolate and syrup in a saucepan and melt over a low heat.
Stir in the crushed digestives (I used my food processor to crush these as I prefer finer crumbs). Set aside around 10 of the Maltesers to crush for decoration and mix the rest of the whole Maltesers in with the digestives and chocolate mixture.
Spread into an 8″/20cm square tin. This one was fairly easy to smooth into the tin. Leave to cool.
Melt the white chocolate in a bowl over a pan of simmering water and pour over the base. Crush the reserved Maltesers and sprinkle over the top.
Leave to set or put in the fridge and then cut into squares.