Cream the softened butter, peanut butter, powdered sugar, and brown sugar until very light, creamy, and smooth.
Add in vanilla extract and salt and mix well.
Gradually add the flour and mix until a soft dough forms.
Add milk a little at a time until the dough becomes soft enough to pipe but still thick (for classic round peanut butter cookies, skip the milk).
Transfer the dough into a piping bag fitted with a large star nozzle and pipe flower shapes on a lined baking tray.
Chill the piped dough in the fridge for 15–20 minutes so they bake neatly without spreading.
Bake in a preheated oven at 160°C (320°F) for 12–15 minutes or until edges look lightly golden.
Allow to cool, then add melted chocolate or a chocolate drop at the center if desired.
