My mother-in-law makes a mean lemon bar - so much so that we served them at our wedding! I decided to jazz them up a bit by adding a chocolate layer, and had a lot of fun experimenting with the wide variety of artisanal chocolate flavors available. (Raspberry turned out great, though a little sweet, and today at the store I noticed a lavender and red salt chocolate bar that might be interesting.) Chili chocolate was the clear winner, though, because the touch of heat and a pinch of added salt really helped balance out the tart, sweet lemon. —TurkeyBeanBacon
Shift the flour and confectioners sugar together in a large bowl.
Cut the butter into the mixture until it is fairly evenly incorporated. The result will look like slightly clumpy, like damp sand.
Spray a 9X13" glass baking dish with nonstick spray and lightly press the mixture into the dish.
Bake the base at 350 degrees for 20-25 minutes, or until it's a golden brown color.
While the base is baking, melt the chocolate over a double boiler (or in a bowl set over a pot of gently boiling water) and add a pinch of salt. I use Taza Guajillo Chili Dark Chocolate, because it has a nice punch, but any chili-flavored dark chocolate will do. Or you could make your own by melting unflavored dark chocolate and adding chili powder, cayenne pepper and salt to taste.
Once the chocolate is melted, use a brush to paint chocolate onto the base until it's completely covered. Don't go crazy though - too much chocolate will overpower the lemon flavor.
Once the dish has cooled a bit, put it in the freezer so that the chocolate can harden up.
Beat together the eggs, granulated sugar and lemon juice in a large bowl. Sift the four and baking power together and stir it into the lemon mixture. Once it's all incorporated, pour it on top of the chocolate-covered base.
Return the dish to the oven for another 20 minutes. You know it's done when you can give the dish a shake and the lemon layer is mostly firm.
Allow to cool completely before cutting (I like to put mine in the fridge overnight and cut the next day). Cut the bars into 2-inch squares. Dust with powdered sugar and cayenne pepper. And, if you're feeling fancy, maybe garnish with a drizzle of chocolate.