Preheat an oven to 180˚C/ 350˚F. Line two baking sheets with baking or parchment paper. Whisk flour, baking soda and salt together and set aside.

Using a stand mixer, hand held mixer or wooden ladle, beat margarine or butter and brown sugar together until combined and pale in colour. Add egg and vanilla essence or extract and mix till combined.

Turn the speed of the stand mixture to low and stir in the flour. Mix till incorporated and fold in pebbles. Mold tablespoon of cookie dough and place on the prepared baking sheet, leaving enough space between them.

Bake for six minutes, remove baking sheet from the oven and lightly press the cookies with your hand or the back of a glass. Place back in the oven and bake for six more minutes.

Cookies will be very soft, let the cookies cool on the baking tray for three minutes. They firm up while cooling. Remove from the baking tray and place on a cooling rack to cool completely.

Cookies can be stored in an airtight container at room temperature for seven days.