Preheat the oven to 375 degrees. Line 3 sheet pans with parchment paper.
Beat the butter, brown sugar, and granulated sugar on medium-high speed for 3 minutes, until light and fluffy.
On low speed, add the vanilla, then the eggs, one at a time.
Mix in the oats.
Slowly add flour, baking soda, salt.
Fold in the chocolate and cranberries until the dough is well mixed. Chill dough an hour or 2.
With a 1¾-inch ice cream scoop (or two spoons), scoop round balls of dough onto the prepared sheet pans.
Sprinkle lightly with fleur de sel.
Bake for 10 to 12 minutes, until nicely browned. Serve warm or at room temperature.
Adapted from Ina Garten