Place the eggs, milk, cream, mustard, and salt in a large bowl. Whisk until frothy. Fold in the shallots, peas, scallions, dill, parsley, and mint. Pour the filling into the pastry shell and transfer to the oven.
4 large eggs, ½ cup heavy cream, ½ cup milk, 1 tbsp Dijon mustard, ¾ tsp kosher salt, 1 cup frozen peas, 3 scallions, ¼ cup fresh dill, ¼ cup flat leaf parsley, 2 tbsp fresh mint