Whisk the flour, cocoa powder, baking soda and salt in a medium-sized mixing bowl until thoroughly combined, then set aside.

Place the oil, brown sugar and granulated sugar in the mixing bowl of an electric stand mixer or a large mixing bowl and using either the electric stand mixer fitted with the paddle attachment or using an electric handheld mixer, beat the oil and sugars together until there are no lumps of brown sugar.

Add in the egg and continue beating until smooth and creamy.

Add in the food coloring, vanilla and vinegar and mix until thoroughly incorporated.

Add the dry ingredients mixture into the wet ingredients mixture slowly, mixing on low (stir) speed just until everything is thoroughly combined (try to avoid over-mixing).

Cover the dough and refrigerate for at least 3-4 hours (cookies will not bake up properly unless the dough is properly chilled and the dough is very sticky and difficult to work with unless it's properly chilled).

When the dough is thoroughly chilled and you're ready to bake the cookies, preheat the oven to 325 degrees F, line baking sheets with parchment paper and place the red sanding sugar/red sugar crystals in a wide, deep bowl or dish.

Scoop dough out using a small cookie scoop and form into balls, then roll each ball in the red sanding sugar until fully coated and place on the parchment-lined baking sheets about 1-2 inches apart (you should be able to have 12 on each baking sheet).

Bake in the preheated oven ~10 minutes, until the cookies have puffed up and the edges are just set (try not to overbake, as cookies will continue cooking as they cool and they taste best when they end up still soft and chewy. If these cookies are overbaked they will end up dry).

Remove the baking sheet from the oven and immediately press a Hershey Kiss/Hug into the center of each cookie. Leave cookies on the tray for about a minute, then remove them to a wire cooling rack and allow to cool completely.

If you want thumbprint cookies, after the cookies have been cooling on the rack for a few minutes, take them and tap them gently on the counter several times to make the Hershey Kiss/Hug collapse down into a pool of melted chocolate in the center. Sometimes the very top of the Hershey Kiss will not be warm enough to melt naturally, so use a toothpick or the tip of a sharp pointed knife to push it down into the center and smooth the top to create the look as shown in the above photo.

If you want the cookies to remain as blossoms (with the Hershey kiss retaining its shape), you must leave the cookies to fully cool (this can take quite some time) before moving them in order to avoid the Hershey kiss losing shape.

Once cookies are cooled, store them in an air-tight container.