Line an 8″ x 8″ or 9″ x 9″ baking pan with foil. Leave an overhang on the sides and spray with nonstick spray. Set aside.
GRAHAM CRACKER CRUST
In a small bowl, blend the graham cracker crumbs, brown sugar, ginger, and cinnamon. Pour in the melted butter, and then mix to combine.
Press the mixture evenly into prepared baking pan, being sure to press firmly. Bake the crust for 10 minutes.
KEY LIME FILLING
In the bowl of a stand mixer fitted with the paddle attachment, or in a medium sized bowl with a handheld mixer, beat cream cheese on high until smooth. Beat in egg yolks one at a time, scraping down the sides as necessary. Beat in sweetened condensed milk, Key lime juice, and lime zest and mix until combined.
Pour filling into prepared crust and bake for 23-25 minutes. Edges should just start to brown and middle should no longer be jiggly. Allow pan to cool at room temperature on a wire rack. When completely cool, chill in the refrigerator for 2 hours, or in the freezer for 1 hour.
When bars are completely chilled, lift out of the pan using foil overhang and cut into squares. Bars can be stored covered in the refrigerator up to 1 week.