Mongoose - getting a single document per value for a given field

For a collection with 200k documents like the following:

{ 
  name: Mario,
  profession: plumber,
  level: 8,
},
{
  name: Luigi,
  profession: plumber,
  level: 5,
},
{
  name: Walter,
  profession: cook,
  level: 10,
},
{
  name: Jesse,
  profession: cook,
  level: 3,
}

What would be an efficient query to get only a single document per profession, with or without sorting by level?

via whyp