Heat the oven and prepare the sheets. Preheat the oven to 350°F (175°C). Line two baking sheets with parchment paper.

Whisk the dry ingredients. In a medium bowl, whisk together the flour, baking soda and salt. Set aside.

Cream the butter, sugars and peanut butter. In a large bowl, beat the butter, brown sugar and granulated sugar together until light and fluffy, about 2 minutes. Beat in the peanut butter until smooth, then beat in the egg, yolk and vanilla.

Add the dry ingredients. Add the flour mixture and stir on low (or by hand) just until no dry flour remains. Do not overmix.

Roll the dough balls. Scoop about 2 tablespoons of dough per cookie and roll into balls. Roll each ball in the extra granulated sugar if you like a sparkly, crisp edge. Place on the prepared sheets, 5 cm (2 inches) apart.

Press the crosshatch. Press each ball flat with a fork: press once, then again at a right angle, to make the classic crosshatch pattern. The cookies should be about 1 cm thick.

Bake. Bake for 10–12 minutes, until the edges are set and lightly golden and the centers still look soft. The cookies will firm up as they cool — do not wait for them to look done in the oven.

Cool and serve. Let the cookies cool on the sheet for 5 minutes, then move to a wire rack to cool completely. Serve at room temperature, or still slightly warm with a glass of milk.