Sift flour, icing sugar and salt in a mixing bowl. Mix with a spatula.
Add in peanut butter and with your hand just combine it into the flour mix.
Add in oil, bit by bit until dough becomes not too sticky or wet but can easily be handled and shaped into a ball. If still crumbly add in a little bit more oil and work from there.
When using your hand to mix in oil, squish everything (the flour/peanut butter mix + oil) together - I find that helps to allow everything to stick and come together nicely.
Pinch off some dough and shape into ball (between 10-12g). Use the end of a chopstick and create an indent at the top (not hole - we don't want a donut). Place on a lined baking tray.
Brush egg wash on top of each cookie. Put into oven for 20 mins at 160C. Allow to cool.