Combine the flour, cocoa powder, baking soda, and salt in a large bowl.
Place the butter, shortening, granulated sugar, and brown sugar in the bowl of a stand mixer. Beat these together for 5 minutes until the mixture is fluffy. Add in the egg and mix. Mix in the vanilla extract and the coffee.
Add half of the dry mixture to the wet mixture. Pulse the mixer a few times to begin to mix. Add the rest of the dry mixture. Pulse the mixer a few more times. Then, stir the cookie together by hand until looks uniform.
Turn the dough out onto a piece of plastic wrap. Wrap the dough up completely. (You can also use a Ziploc bag or a covered container.) Chill the dough overnight, or at least 8 hours.
Bake the cookies:
Preheat the oven to 350° F. Line a baking sheet with parchment paper.
Scoop tablespoon-size portions of the dough, and lightly roll them in your hands before putting them on the baking sheet. Space the dough balls about 2 inches apart.
Bake the cookies for 14-15 minutes, until the edges are just set. Remove them to a cooling rack to cool completely.
Prepare the buttercream, in advance or while the cookies cool:
Blend together the ⅓ cup of softened butter and the remaining teaspoon of vanilla extract. Add in the confectioner’s sugar and beat the ingredients together.
With the mixer running add the food coloring. Add in the milk just a little at a time. Keep beating the frosting and adding milk little by little until the frosting reaches a good consistency: fluffy and not too stiff.
If the frosting is not red enough mix a few more drops into it until you have the shade you like - try to have it be close to the shade of red in your fondant.
Sandwich the cookies and buttercream:
Make cookie sandwiches by spreading 1 tablespoon of buttercream on the bottom of one cookie and pressing the bottom side of another cookie together with it. Press the cookies together just enough so that the frosting spreads out to be even with the edges of the cookies. (This will help the sides look smooth when they are coated in chocolate.)
Make sandwiches with all of the cookies.
Coat the cookies:
In a bowl in the microwave oven or in the top of a double-boiler on the stovetop, melt the chocolate chips with the vegetable shortening, stirring them together until the mixture is completely smooth.
Set a cooling rack set over a parchment paper-lined surface. Have your cookie sandwiches, melted chocolate, a large spoon, and a fork ready. You will also need a utensil to hold the cookies: I like to use a potato masher that when held pointing down has a flat surface where the cookie can sit. Or, use a large slotted spoon or a large fork: something that will allow excess chocolate to drip away.
Place a cookie on the potato masher or utensil, hold it over the bowl of melted chocolate, and use a large spoon to spoon the chocolate over the cookie. Be sure to spoon it over all of the exposed cookie including the sides and around the bottom edge.
When the cookie is coated push it off the potato masher onto the cooling rack - you can do this by sliding the fork under the cookie to move it onto the rack.
Repeat these coating steps with all of the cookie sandwiches. Allow them to set at room temperature until the chocolate is firm - the time will vary depending on how warm your kitchen is, but you can aim a small fan at the cookies to speed the process along.
Roll and cut the fondant:
Roll out the fondant to a ¼-inch thickness. Use a tiny bit of confectioner’s sugar on your work surface if the fondant is sticking. Use a sharp knife and a ruler to make straight cuts, and slice the fondant into 1-inch x 2-inch rectangles. (I do this by first cutting the fondant into 1-inch thick strips and then slice these strips into 2-inch long sections.)
When you have enough rectangles (one for each of your cookie sandwiches) slice through each rectangle corner to corner, like a giant X through the middle.
You'll use the triangles from the shorter sides - the flatter triangles can be discarded (or eaten sneakily while you work.)
Place two triangles on the top of a cookie sandwich in the center, so that the points are touching and form an hourglass shape - like the marking on a black widow spider! If the triangles are not sticking to the cookie you can moisten the backsides slightly with water and this will help them stick.
Place fondant triangles in the hourglass pattern on each of the cookies. They are now ready to serve. Or more fittingly for Black Widow, they are now ready to kick ass.
These cookies can be stored covered in a container deep enough that the tops won’t be smudged or mussed, for up to three days. Makes about 18 cookie sandwiches.
Let the dough chill for 8 hours or overnight. This gives the dough time to come together, and to make it easier to handle when scooping them to bake.
If you need some shortcuts, you can use purchased chocolate cookies instead of baking your own. Same goes for the frosting: just get store-bought and add red food coloring to it. But trust me: homemade cookies and buttercream taste so much better!