To cook beet, bake in oven at 400 degrees Fahrenheit for 1 hour or more, depending on its size. The beet will become soft and wrinkled. Let it cook and remove the peel. It will be easy once the beet is cooked. Cut tofu into small cubic or rectangular slices about ¼-inch thick. Put beet and corn in a blender and mix until a paste is formed. Put about 1 teaspoon of beet-corn paste on a tofu slice, then cover it with another slice. Repeat until all tofu is used up. Serve on a plate, garnish with watercress.