Brew Potion

Upon casting this spell, select from your list of prepared 1st level spells with the following properties;

• Has a casting time of 1 action or 1 bonus action.
• Requires a target or has a range of Self.
• Doesn't require an attack roll. 

You then conjure or imbue an existing drinkable liquid with the effects of the selected spell. for spells such as enlarge/reduce or polymorph, the effects are chosen by the drinker. If the spell were to require concentration, the drinker must concentrate on the spell. Finally, even if the spell could effect multiple targets, such as the bless spell, it will only effect the drinker. After 24 hours, or upon casting the spell again without upcasting it, the potion reverts to its original contents or just fresh water. If you can up cast this spell, you may have an additional potion made, up to one per spell level of 1st through 4th.

Using a Higher-Level Spell Slot.  You may select a prepared spell of up to half the slot used, rounded down, so 2nd for a 4th level slot, 3rd for a 6th and 4th for an 8th.