Preheat your oven to 350°F (175°C) to ensure even baking.
Line your baking sheet with parchment paper to prevent sticking.
In a medium bowl, combine rolled oats, flour, baking powder, baking soda, and salt. Whisk until well mixed.
In a large bowl, cream the butter and dark brown sugar until light and fluffy (about 2-3 minutes).
Beat in the egg and vanilla extract until fully incorporated.
Gradually add the dry ingredients to the wet mixture, mixing until just combined.
Fold in the chopped pecans and raisins (or currants) using a spatula.
Drop rounded balls of dough onto the prepared baking sheet, spacing them about 2 inches apart.
Bake for 10-12 minutes, until the edges are lightly golden. The centers may look underbaked.
Allow to cool on the baking sheet for about 5 minutes before transferring to a cooling rack.
