Line a baking tin with baking paper. Leave a little excess paper sticking out to help you remove it from the tin later.
Crush the digestives - you can either use a food processor or place them in a food safe bag and bash with a rolling pin.
Melt the milk chocolate, syrup and butter together. You can either do this in a microwave in short bursts or in a saucepan on the hob. Just make sure to stir it regularly and don't let the chocolate burn.
Once the mixture is melted, combine it with the crushed biscuits and maltesers and mix together. Make sure it is fully combined.
Pour the mixture into the lined tin and smooth it out with the back of a spoon or a spatula.
Place in the fridge to set while you make the topping.
For the topping, crush the remaining maltesers roughly - place in a bowl and gently crush with a rolling pin or wooden spoon. You can also leave them whole if you prefer.
Melt the white chocolate. You can do this in the microwave or in a heatproof bowl placed over a saucepan of simmering water.
Remove the traybake from the fridge and pour the melted white chocolate over the top. Use a spatula or spoon to smooth it out. Decorate by sprinkling with crushed maltesers or placing whole maltesers on top.
Place in the fridge and leave to set for a minimum of 2 hours.
To cut, remove from the fridge, take out of the baking tin and let it sit for 10 minutes to soften at room temperature. Use a sharp knife run under hot water to cut into slices.