Preheat and prepare your tray. Set your oven to 180°C (fan-assisted) or 200°C conventional. Line two baking sheets with parchment paper — this guarantees no sticking and makes cleanup even faster.

Cream the butter, peanut butter, and sugar. In a large mixing bowl, beat the softened butter, peanut butter, and brown sugar together with a wooden spoon or electric mixer until the mixture looks pale, fluffy, and noticeably lighter in colour — about 2 minutes. You’ll smell the sweet peanut aroma rising up.

Add the wet ingredients. Crack in the egg and pour in the vanilla extract. Stir until the mixture is glossy, smooth, and fully combined. The batter should feel thick and slightly sticky when you lift the spoon.

Fold in the dry ingredients. Sift the plain flour, bicarbonate of soda, and salt over the wet mixture. Fold gently with a spatula until just combined — stop as soon as you no longer see streaks of white flour. Overmixing will make the cookies tough.

Shape the dough balls. Using a tablespoon or a small cookie scoop, portion out rounded balls of dough, about 35g each. Roll them between your palms until smooth — the dough will feel slightly greasy but should hold its shape easily.

Create the classic criss-cross pattern (optional). Place the dough balls on the prepared trays, spacing them about 5cm apart. Dip a fork in cold water, then press down gently on each ball to flatten it slightly and create the iconic criss-cross marks. The edges will crack a little — that’s exactly what you want.

Bake until just set. Slide the trays into the oven and bake for 9–11 minutes. The cookies will look puffed, lightly golden around the edges, and still soft and slightly underdone in the centre. They should smell deeply of toasted peanuts and brown sugar.

Cool on the tray. Let the cookies rest on the baking sheet for 5 minutes — they will continue to set as they cool. The centres will sink slightly, becoming tender and fudgy. Transfer to a wire rack to cool completely, or serve warm for maximum softness.