Fairly nice and quaint. A few suggestions from me on how to improve things. Firstly sound, the music is overly repetitive, and has a harsh static at the end of the loop which makes things unpleasant. Maybe also change the music when engaging with the shop keeper.
Second, possibly see if you can add mumbles or talks when buying things or selling to customers. Just hearing the sound of coins can get boring real quick. Make sure to vary pitch and tone of the coins and mutterings of shopkeeper and customers.
Lastly, collision with the cauldron has been a primary problem. Half the time I thought I put the ingredient in simply by dragging in from the side. Maybe make the collision boxes of the ingredients larger, or more clearly defined. Maybe a pool of water in the cauldron to indicate that you should drop them in rather than drag them to the cauldron. Another possible way to indicate that the player isn't putting the ingredient in correctly could be the sound of a metal clink when the object strikes the side of the cauldron, or a plant brush sound. Experiment with sticks, leaves, flowers, and metal on cast iron pots if you have access to them.
Otherwise, lovely game that reminds me of Potioncrafter.