For people who are having problems with the glass, it's very important you have a candy thermometer. The sugar should be cooked on low, cooking it too fast or too hot will cause it to carmelize. I start on low and ramp it up to nearly medium over the course of an hour and my glass comes out nice and clear. It's a time commitment, but there's really no way to rush sugar. This a fun recipe that will get you kudos every time though!
Prepare Red Velvet Cake Mix According to box, line cupcake tins with paper cupcake liners.
Divide cake batter between lined cupcake tins.
Bake according to box instructions. Let cool and frost cupcakes with white frosting.
Make the sugar glass. Mix 2 cups water, 1 cup corn syrup, white sugar, and cream of tartar in a large saucepan; bring to a boil. Use a candy thermometer and boil sugar syrup until temperature reaches 300 degrees (hard ball), stirring constantly. The mixture will thicken as water evaporates. When sugar reaches 300 degrees, quickly pour onto a metal baking pan. Cool until completely hardened. Break into "shards" using a meat mallet.
Make the edible blood. Mix together 1/2 cup corn syrup and cornstarch in a large bowl. Slowly stir in the 1/4 cup of water, adding more if necessary, until the corn syrup mixture has thickened to the consistency of blood. Stir in the red and blue food coloring.
Stab each frosted cupcake with a few shards of broken sugar glass. Drizzle on drops of "blood" to complete the effect.