Melt the butter and chocolate in a pan on a low heat until smooth and combined, stirring occasionally.
Remove from the heat and stir in the condensed milk, followed by the almonds and Horlicks.
Sift in the flour and a pinch of sea salt, mix together, then chill in the fridge for 20 to 30 minutes (no longer).
Once cool, but still pliable, smash up the Maltesers and roughly chop the white chocolate, then mix it all together.
Preheat the oven to 170°C/325°F/gas 3.
Divide the mixture into 24 equal-sized balls and place on a couple of large baking trays lined with greaseproof paper.
Flatten each a little – like squashed golf balls (you can freeze them at this stage to bake another day if you like) – then bake for around 12 minutes, or until chewy in the middle and firm at the edges. Leave to sit in the tray for 5 minutes, then transfer to a wire rack to cool.
If you want to take these devilish cookies to another level, either sandwich 2 cookies with a good spoonful of your favourite ice cream, or even some homemade marshmallow, and squeeze… heaven, or simply drizzle all the cookies with melted chocolate while they cool… amazing!
