Combine endive, spinach, tomatoes, and mint in bowl and distribute evenly.
TO MAKE THE DRESSING: Chop the shallots and add to the vinegar with the salt. Let sit for 5 minutes. Whisk in the olive oil. Add black pepper to taste.
Dress salad as heavy or as lightly as you like. Either add the feta cheese to each individual plate or add with the rest of the salad ingredients and distributing cheese throughout being careful not to moosh cheese.