Preheat your oven to 325°F. In the bowl of a stand mixer fitted with the paddle attachment or a large bowl and a hand mixer, beat the butter until light and fluffy. Add the sugar and vanilla, and beat until well combined. In a small bowl, place the flour, baking powder and salt, and whisk to combine well.

Divide the dough in half, and place one piece on a large sheet of unbleached parchment paper.

Pat it into a thick rectangle. Dust lightly with all purpose flour and roll the dough into a 12-inch x 5-inch rectangle, a bit more than 1/8-inch thick (no thinner), sprinkling lightly with flour as necessary to prevent sticking.

Square the edges of the dough as best you can. Place the rectangle of dough, still on the parchment paper, flat on a half sheet pan.

Have a sharp knife, pizza wheel or pastry wheel ready to score the dough as soon as it is baked.

Place the dough in the center of the preheated oven and bake until very pale golden all over, about 12 minutes.

Remove from the oven, and immediately score into smaller rectangles of about 1/2-inch wide x 3-inches long.

Allow to cool completely, and break the cooled wafers along the scoring.

Repeat with the other piece of dough.

Place the chocolate and coconut oil or shortening in a medium-size, heat-safe bowl and melt either in the microwave in 30-second bursts, stirring in between, or over a double boiler until melted and smooth.

To make the candy, you will need 6 rectangular wafers per 3-finger candy bar.

In each finger of a Kit Kat mold, if you have one, pour a thin layer of melted milk chocolate in the bottom of each well. Layer one rectangular wafer on top of the chocolate in each well, cover with another layer of melted chocolate, then followed by another wafer. Finish with a thick layer of chocolate to the top of the mold.

Shake the mold gently back and forth to distribute the chocolate evenly without shifting the wafers around. Allow the chocolate to set completely in the molds before popping out the candy.