Mexican Sweet Potato Candy

Combine the sugar, milk, butter, and salt in a 2-liter saucepan. Cook over low heat, stirring occasionally, until the sugar is dissolved. Wash the sugar crystals that have formed on the sides of the mold using a brush dipped in cold water.Continue cooking, stirring occasionally, until the mixture is firm as a ball (244 °). Remove from heat; cool to warm (110 °). Add the sweet potatoes; beat on medium speed with an electric mixer until the mixture thickens. Add the pecans. Place the candies on a well-oiled large serving platter. Cool and cut into 1-inch-thick squares.