Smashing the peanut butter cookies with a fork before baking helps them bake evenly. Peanut butter cookies don’t spread out as much as other cookies, so we need to give them a bit of “help” by flattening them into an even surface first. See the comparison below between cookies that were pressed with a fork, vs cookies that were dropped directly onto the baking sheet. The fork cookies look neater and they have the classic peanut butter cookie appearance.