Hydrate the raisins in boiling water for 10min. After that time remove the water and pat dry the raisins.
Place the flour, sugar, baking powder, salt and butter in a bowl. Pinch the butter with your fingers mixing it with the rest of the ingredients until you get a texture that looks like wet sand and there are no large lumps of butter. If you feel that your hands are always really warm you might want to hold an ice cube for a while before you do this. This step can also be done in a food processor.
Add the milk and mix in using a spatula until it doesn't help anymore. Finish to incorporate the ingredients by mixing with your hands.
Add the raisins and make sure they're nicely mixed by using your hands. Don't knead, though! We're just making sure everything is incorporated. If you knead it will turn tough.
Wrap in cling film (flatten out the dough, don't make a ball) and place in the fridge for 30min.
Take it out and roll it out on a floured surface until it's 2cm or 3/4in thick.
Cut them however you like: triangles, circles, hearts, etc. When you're bringing the scraps of dough together to stretch it again make sure you mix it nicely. This dough is quite flaky so it's a bit stubborn when you're trying to mix it and wants to divide up again.
Bake in a preheated oven at 180C / 350F on a baking tray with baking paper or silpat for 20-30min or until golden.