Bottom Chocolate Layer:
Line bottom of 15-1/2 x 10-1/2 x 1-inch jelly-roll pan with aluminum foil.
Melt 1 cup chocolate
and 2 tablespoons shortening in top of double boiler over hot, not boiling water, until smooth. Pour in prepared pan, spreading evenly with long thin metal spatula. Refrigerate about 20 minutes, until firm.
Tape waxed paper to bottom of second 15-1/2 x 10-1/2 x 1-inch jelly-roll pan. Invert chocolate onto paper. Peel off foil. Refrigerate.
Combine marshmallow cream, 4-1/4 cups powdered sugar, orange rind and extract, and salt in medium-size bowl
. Stir with wooden spoon until thick mass forms (knead mixture with hands if necessary to incorporate ingredients).
Lightly dust work surface with a little of remaining 3/4 cup powdered sugar. Turn marshmallow mixture out onto prepared surface. Knead until smooth, about 2 to 3 minutes.
Tape waxed paper to bottom of first jelly-roll pan. Lightly dust paper and rolling pin with remaining confectioners sugar. Roll filling out to 1/8- to 1/4-inch thickness, to size of jelly-roll pan.
Top Chocolate Layer:
Remove sheet of chocolate from refrigerator. Let stand to soften slightly, about 5 minutes. Carefully invert filling on top of chocolate; peel off waxed paper. Return to refrigerator and chill 15 minutes.
Melt together remaining chocolate and shortening in top of double boiler over hot, not boiling water, until smooth. Remove filling from refrigerator. Pour chocolate over top, smoothing over entire surface with long thin metal spatula. Return to refrigerator and chill 15 to 20 minutes or until firm enough to cut.
Using 1-1/2- to 2-inch mini cookie cutters, cut into simple shapes. Or cut into 1-inch squares. Refrigerate until serving.