Preheat the oven to 350°F. In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.

Place the butter and brown sugar in the bowl of a stand mixer. Mix on medium speed until light and fluffy, about 2-3 minutes. Mix in the golden syrup and vanilla until fully incorporated.

Add the dry ingredients to the butter mixture and mix on low until the dough begins to clump and resemble wet sand (it will hold together when you squeeze it with your hand). Gently knead the dough with your hands to bring it together.

Divide the dough into two portions. Shape each portion into a rough log shape and place on a piece of parchment paper (though dough may be a bit crumbly at this point which is fine). Cover the logs with plastic wrap or another piece of parchment. Using a rolling pin, roll each log into an oval about 12 inches long and ¼ inch thick. Sprinkle evenly with pearl sugar, cover with plastic wrap again and gently roll the pin over once or twice more to slightly imbed the pearl sugar into the dough.

Remove plastic wrap and transfer the parchment with the ovals on it to a rimmed baking sheet. Bake for 12–14 minutes, or until the logs are lightly golden and set but still soft in the center. Remove from the oven and let cool for 2–3 minutes. Using a sharp knife or pizza wheel, cut the logs diagonally into 1-inch slices. Transfer the cookies to a rack to cool.