Preheat oven to 300 degrees F. Grease a 9x13 baking dish.
In a bowl, cream together the butter and almond paste with an electric mixer. Add sugar and eggs until combined.
Sift together the flour and salt and add to mixture. Mix until combined.
Press into the prepared baking dish.
Bake for 1 hour until lightly browned and center is firm.
Add the powdered sugar, almond extract and three tablespoons milk into a small bowl. Mix until smooth, adding the additional one tablespoon milk, if needed.
Spread glaze over hot bars right out of the oven. Once cooled, slice and serve.
