Source: toldeoblade.com - from Great Cookies

Crust
6 tablespoons (3/4 stick) unsalted butter
1 1/2 cups graham cracker crumbs (7 to 8 whole graham crackers)
2 1/2 tablespoons granulated sugar

Filling
3 large egg yolks
1 (14-ounce) can sweetened condensed milk
1/2 cup Key lime juice
2 teaspoons freshly grated lime zest
3/4 cup lightly crushed toasted sweetened flaked coconut

Position rack in center of oven; preheat oven to 350 degrees F. Cut a 14-inch square of foil for an 8-inch square pan. Invert pan and center foil over pan, pressing it across bottom and down sides. Remove foil, turn pan right side up and place foil shell in pan, shaping it smoothly across bottom and snugly against sides of pan. Butter and flour foil (baking spray can be used as well).

To make the crust: Melt butter. Cool until tepid. Add crumbs and sugar. Stir to combine well. Sprinkle half crumb mixture into pan. Press crumbs evenly using bottom of glass. Bake 7 to 8 minutes or until just set.

To make the filling: Beat yolks on medium-high until slightly thickened and lightened in color, 3 to 4 minutes. Slowly add milk, and beat 4 to 5 minutes longer. Reduce mixer speed to medium-low, and mix in juice and zest. Let crust rest for 2 or 3 minutes before pouring half the filling over it. (Give pan several taps on a hard surface to spread filling evenly.) Return to oven and bake for 9 to 10 minutes, until set on top. Sprinkle remaining crumbs over filling, spreading them carefully and pressing gently with bottom of a glass. Bake for 8 to 9 minutes, or until set. Let rest for 2 or 3 minutes. Pour remaining filling over crust, spreading evenly with back of a tablespoon. Tap pan on counter to even filling. Bake for 10 minutes, or until set.

Let stand for 2 or 3 minutes, then sprinkle with half the toasted coconut, pressing it in gently. Then top with remaining coconut. Refrigerate for 4 to 5 hours before removing from the pan.

Remove the cookies from the pan, and roll down the foil. With a sharp knife, cut the cookies into 25 squares.

Yields 25 (1 1/4-inch) squares

Per square: 121 calories (percent of calories from fat, 44), 2 grams protein, 15 grams carbohydrates, trace fiber, 6 grams fat (4 grams saturated), 38 milligrams cholesterol, 58 milligrams sodium