Put the peanut butter, sugar, egg, bicarbonate of soda and salt in a large bowl and mix with a wooden spoon until thoroughly combined. Mix in the chocolate chips.
Take rounded tablespoons of the mixture and roll into balls. It helps to dip the spoon in water every couple of cookies. Put the balls on baking sheets, spaced 5 cm (2 in) apart. Flatten the balls slightly with your fingers and bake for 12–15 minutes. The cookies should have spread out to around 1/2 cm (1/6 in) thick and have a slightly cracked surface.
Allow the cookies to cool on the baking sheet for 10 minutes before carefully transferring to a wire rack, using a spatula or palette knife. Cool thoroughly and store in an airtight tin for up to 3 days or freeze. If frozen, defrost by spreading out on a baking sheet or plate at room temperature for 30 minutes.