Add the dry ingredients into the wet and keep stirring until dough all comes together. I like using a rubber spatula and folding into the dough to get it to come together for a minute or 2. Dough will be thick, but should not be crumbly.
Transfer the batter into the prepared pan, and smooth down evenly with a spatula, spoon or use fingertips.
When you take the peanut butter bars out, the top will look set but they will still be very undercooked underneath, which is what you want. Leave them to cool for at least 20 minutes, during which time they will firm up.