Question

how can I write a
dialogue between mother and son about making pudding

Answer 1

You can write this dialogue by using either your pen or your pencil as simple as that

but your dialogue should be like

son : mom I want to eat pudding today

mom : Okay son, come help me with it. what type of pudding do you want?

son : I want a chocolate pudding

and thus this conversation will go on the mother asks him to bring chocolate from the market etc etc