Preheat the oven to 160C/140C Fan/Gas 3.
Line two baking sheets with baking parchment. On one of the sheets spread out the desiccated coconut and put it under a medium grill for a couple of minutes until the coconut starts to brown.
Tip the toasted coconut into a large bowl and set the baking tray aside for later (you can reuse the same sheet of baking parchment).
Add the condensed milk, vanilla extract and bicarbonate of soda into the coconut and mix until thoroughly combined. It should be thick and quite difficult to stir.
Take the coconut mixture in your hands and shape 15 balls. If it feels like it won't hold its shape add more desiccated coconut a tablespoon at a time until it feels firm but pliable. N.B make more balls if you want smaller bite-sized macaroons.
Arrange the balls on the prepared baking sheets, flatten with the palm of your hand and leave an inch gap as they will spread during cooking. N.B For ball-shaped macaroons use an ice cream scoop to tightly pack the mixture and drop it onto your baking sheets, skip the flattening part!
Bake for around 15 minutes or until brown and toasted on the outside and remove from the oven. The macaroons will still have a slight 'wobble' at this point but will firm up as they cool.
To make the icing, put the icing sugar into a bowl and add cold water a tablespoon at a time until you have the right consistency, add the rose syrup a few drops at a time. You might find you want to add less than a teaspoon if you want a paler pink. The rose flavouring can be quite potent so use it sparingly. The icing should be runny enough to drizzle on top but not so runny it slides off.
Transfer the coconut macaroons to a wire rack to cool completely then drizzle the icing on top then add a sprinkling of pistachios.
Dust with icing sugar to serve.