1 Can white frosting
1 Box Red Velvet Cake Mix
2 cups water
1 cup light corn syrup
3 1/2 cups white sugar
1/4 teaspoon cream of tartar
1/2 cup light corn syrup
1 tablespoon cornstarch
1/4 cup water, or more as needed
15 drops red food coloring
3 drops blue food coloring
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.