Preheat your oven to 350. Prepare two baking sheets for nonstick.
In a medium bowl, use a whisk or a fork to mix together the flour, ginger, cinnamon, and baking soda.
Next, in a mixing bowl, beat together the butter and the two sugars until creamy. Then beat in the molasses, egg, and food coloring.
Add half of the dry ingredients to the bowl, mix, scrape down the sides of the bowl, and then mix in the remaining dry ingredients to the mixing bowl.
Use a two inch cookie scoop to scoop out the dough, roll the dough into balls, and then press the balls into the baking sheets. Bake the cookies for 10 minute or until the edges are crisp. The allow the cookies to cool for 15 minutes on the baking sheets before transferring to a cooling rack. While the cookies are cooling, press an edible heart into the center of half of the cookies.
When the cookies have fully cooled, you can assemble the sandwiches. Combine together the powdered sugar and shortening until creamy, You can add a teaspoon or two of water or milk to get a more spreadable consistency if needed.
To assemble the cookies simply place about a tablespoon of filling on the inside (flat side) of the cookies without a heart. Then press the heart cookies on top, with the heart facing you.