Beat the butter and both sugars together with an electric mixer in a mixing bowl for a few minutes until thick and combined, then beat in the egg and vanilla for a minute or so until light.
Whisk the oats, flour, cinnamon, baking soda and salt in a bowl, then add to the mixing bowl along with the grated carrot and raisins and mix, by hand, gently until combined.
Cover the bowl and chill the dough in the fridge for at least 1 hour.
Preheat the oven to 350°F / 175°C and line two baking sheets with parchment paper.
Drop heaped tablespoonfuls of the dough onto the baking sheets an inch apart.
Bake the carrot cookies for 12-15 minutes or until the edges begin to turn brown. Allow to cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.
Store in an airtight container at room temperature for up to 1 week.