Preheat oven to 400 degrees. Coat the sides and bottom of a cast iron skillet with butter.
Wash and pick through berries. In a medium bowl, toss together the blueberries, lemon juice, liqueur, flour, and sugar. Pour berries in prepared skillet.
In a medium bowl, add flour, sugar, and cut in shortening until mixture resembles a coarse meal. Add egg and milk until soft dough forms. Drop dough by tablespoons on top of berries. Bake until blueberry mixture bubbles and topping is golden brown and cooked through, about 20-25 minutes.