Preheat the oven to 350°. Line a baking sheet with parchment paper.
In a medium bowl, whisk together flour, baking powder, and baking soda.
In the bowl of an electric mixer, cream the butter and sugars until fluffy (about 3 minutes).
Beat in egg and golden syrup.
Gradually add flour mixture until incorporated.
Stir in oats and toffee bits.
Allow the dough to rest for 10 minutes so that the oats will absorb some moisture.
Use a cookie scoop to place dough balls at least 2” apart on the prepared baking sheet.
Bake for 12-15 minutes or until the cookies are golden brown all over.
Cool on the baking sheet for 5-10 minutes before transferring to a wire rack to cool completely.
Store in an airtight container at room temperature for up to one week.