In a medium bowl, mix graham cracker crumbs and 3 tbs. sugar. Blend in butter until well-mixed. Press evenly into the bottom of a 9" springform pan.
Beat eggs in a large mixing bowl until light, fluffy and lemon-colored. Gradually add 1 cup sugar, flour, mace and nutmeg, beating thoroughly until well-blended. Add ricotta and mix well. Fold in 2 cups blueberries with a rubber spatula.
Pour into prepared pan with crust and place pan in a bain-marie. Bake for about 1 hour and 15 minutes, or until cheesecake is set (center should still be slightly wobbly). Turn off the heat and allow cheesecake to stand in the oven for 20 more minutes.
Carefully remove from oven. Take cheesecake pan out of bain-marie and cool in pan on a wire rack. When cool, move pan to the refrigerator and chill overnight.
Before serving, remove sides of pan and slice. Garnish each slice with extra blueberries and mint leaves, if desired.