Cut shortening into flour and salt. Dissolve sugar in warm water and beat into flour to form a pie dough. Knead well, then cut into 4 pieces. Knead each piece again then cover and set aside for 1 hour.
Drain ricotta in a colander, cover and refrigerate for 2 days. Should feel dry to the touch. Mix all ingredients well and set aside. Roll dough to 1/8" thickness. Cut into 3 1/2" squares. Brush squares with egg white. Fill center with 1 Tbsp. of ricotta, fold dough over to make a triangle. Seal edges with the tines of a fork. Prick top. Placed filled triangles on a floured cloth. Heat oil. Place Cassetelle gently in hot oil. Do not crowd. When edges are gold in color, turn and carefully fry on other side. Remove, drain on paper towels. Dust with confectioner's sugar to serve.