Beat the softened butter in a large mixing bowl until smooth and creamy. Add the granulated sugar and light brown sugar, then mix until the texture becomes light, fluffy, and well combined.

Stir in the peanut butter until smooth, then add the egg and mix again until fully incorporated and glossy.

In a separate bowl, whisk together the plain flour, baking soda, baking powder, and salt. Gradually add the dry ingredients to the wet mixture, gently folding until a soft dough forms. Mix only until combined to keep the cookies tender.

Shape the dough into a flat disc, wrap well, and chill in the refrigerator for at least 2-4 hours, or up to 24 hours. This step helps develop flavor and gives the cookies their signature crinkle texture.

Preheat the oven to 190°C (375°F) and line or prepare your cookie sheets.

Roll the chilled dough into small balls about 3 cm (1¼ inch) wide and place them on the baking trays, leaving space between each cookie for spreading.

Bake one tray at a time on the centre rack for 9-11 minutes, until the edges are lightly golden and the tops look soft with natural cracks.

Let the cookies rest on the tray for about 1 minute, then transfer them to a wire rack to cool completely before serving. Repeat with the remaining dough.