Preheat your oven to 325°F. Line rimmed baking sheets with unbleached parchment paper and set them aside.

In a large bowl, place the cake flour, salt and sugar, and whisk to combine well.

Create a well in the center of the dry ingredients, add the butter and 1 tablespoon of the water, and knead until the dough comes together, using more water by the teaspoon if necessary.

Place the dough between two sheets of unbleached parchment paper and roll into a rectangle about 1/2 inch thick.

With a sharp knife or pizza or pastry wheel, slice into rectangles 3 1/2 inches long and 1/2 inch wide.

Place the rectangles 1 inch apart from one another on the prepared baking sheets. Using a toothpick or wooden skewer, press three holes, evenly spaces apart and each about 1/8 inch deep, into the top of each dough rectangle.

Place the baking sheets in the center of the preheated oven and bake for about 10 minutes, or until just beginning to brown on the edges. Remove from the oven and allow to cool completely on the baking sheets.

Line a quarter sheet (13 x 9 x 1-inch) pan with unbleached parchment paper and set it aside. In a medium-size, heavy-bottomed saucepan, place the sugar, water and cream of tartar and whisk to combine.

Clip a candy thermometer to the side of the saucepan and cook, undisturbed, over medium-high heat until the sugar begins to turn amber-colored around the edges and reaches 300°F.

Remove the saucepan from the heat, stir to prevent the sugar from burning, and add the cream. The mixture will bubble up quite a lot. Stir until the bubbling subsides. The sugar may seize up, but it will melt again.

Add the butter and stir to combine. Return the saucepan to the heat and cook, undisturbed, over medium-high heat until the mixture reaches 245°F. Remove from the heat and whisk in the vanilla.

Pour the hot caramel into the prepared pan and shake it back and forth and side to side into an even layer.

Allow to sit at room temperature until set, at least 2 hours.

Once cool, the caramel can be covered in plastic and stored in a cool, dry place for up to a month.

Roll out the cooled caramel between two sheets of unbleached parchment paper into a rectangle about 1/2 inch thick.

With a sharp knife or pizza or pastry wheel, cut the caramel into 3 1/2 x 1/2-inch rectangles (the same size as the shortbread cookies).

Place one caramel rectangle on top of each cooled shortbread cookie, and press gently to adhere.

Place the chocolate and coconut oil in a large, microwave-safe bowl and melt in 45 second bursts at 60% power, stirring in between, until melted and smooth.

Allow the chocolate to sit at room temperature until it begins to thicken a bit. Immerse the caramel-topped shortbread, one at a time, in the chocolate.

Pull the bar out of the chocolate by slipping the fork under it and bobbing it on the surface of the chocolate a few times before pulling it along the edge of the bowl and carefully placing it on a clean sheet of waxed or parchment paper.

Allow the chocolate glaze to set at room temperature.