The butter at room temperature melts partially, then with the mixer it mixes until it thickens again and becomes like a cream.
Add the sugar and vanilla essence and mix until the sugar melts and becomes a frothy cream.
Add the egg and mix until completely incorporated.
Then pour the flour and mix with a spoon.
The composition is poured into a posh and small piles are sprung, at a distance from each other.
Put them in the preheated oven at 170 degrees for 10-15 minutes, until the sole of the cookie browns slightly.
Remove and leave to cool.