1. Beat butter in a medium bowl with an electric mixer on medium to high speed for 30 seconds. Add sugar and baking soda; beat till combined. Beat in egg yolk and vanilla. Beat in as much of the flour as you can with the mixer. Stir in any remaining flour with a wooden spoon.
2. To shape, press a small amount of dough firmly and evenly into a teaspoon (not a measuring teaspoon). Gently tap the side of the spoon onto a greased cookie sheet to remove the shaped cookie. If necessary, use your finger to help remove dough from spoon. Reshape dough slightly on cookie sheet, if necessary. Makes 32 ovals.
3. Bake in 350 degree oven for 8 to 10 minutes or till lightly browned. Cool on cookie sheet. Combine chocolate and shortening in a small saucepan. Cook and stir over low heat till chocolate is melted; cool.
4. Place about 1 teaspoon strawberry jam or hazelnut butter on the flat side of a cookie; top with another cookie, flat side down. Repeat with remaining cookies. Dip wide end of each cookie sandwich into melted chocolate. Place on wire rack over waxed paper. Sprinkle with chopped nuts. Insert a pretzel piece at top of cookie for stem, if desired.
5. To store, place cookies in a single layer in a shallow container; refrigerate up to a week.
not a measuring teaspoon.