"As Baba Yaga, successfully hit an enemy god with a brewed potion that uses 5 of the same type of ingredient"
This is currently positively glitched.
At the moment you DO NOT need to level this up fully and only need 3 of the same ingredient, not 5 as the description states.
Baba Yaga's second ability, Baba's Brew, is the ability you need for this. Baba Yaga throws together random ingredients to brew a Potion. There are three possible ingredients, Eye of Newt, Dragon Scale and Wolf Tooth.
Each potion has a random mixture of these three ingredients. At the first level of this ability, you only have 3 max ingredients. You need to max this ability out to get 5 ingredients in a single potion. At max level, you need to make a potion that has 5 of the same ingredient (e.g. 5 Dragon Scales)
You'll randomly make a potion that has all 5 of the same type of ingredient at somepoint. Keep an eye out on the potion you make (it'll have 5 dots of the same colour (red, blue or green) and make sure you hit an enemy with it.
Hit an enemy god with a potion that has all 5 ingredients slots the same, and you'll pop this achievement.
As an aside, you can store a single potion for use later, so if you aren't sure you can make the shot and hit an enemy god, you can save a potion for later and then throw it out at any time. If you cancel your ability, the potion will be saved in a consumable slot (where you'd normally find wards or potions)
I'd recommend building cooldown reduction for this, purely to be able to throw more brews and increase your chances of getting a perfect brew.