Instructions: 1. In a food processor or with an electric mixer, cream together the butter and sugar. Add egg yolk and vanilla and mix till smooth. Add flour and baking powder, stirring baking powder in slightly to distribute it, and pulse or beat until flour is incorporated. Stir nuts in by hand. Turn out onto 2 sheets of plastic wrap and form two 6" logs. Wrap well and refrigerate for at least 2 hours or up to 3 days. Dough can be frozen for one month.

2. Preheat oven to 350 F. Using a sharp knife, cut chilled dough into rounds 1/4" thick. Arrange 1-inch apart on ungreased cookie sheets, reshaping into rounds if needed. Bake 10-12 minutes, until edges are lightly browned and cookies are pale golden. Cool on a rack.

3. To make glaze, melt chocolate with oil. Dip with one half of each cookie. Roll glazed edges in chopped pistachios. Let stand for 2 hours or until glaze has set. Store covered for 2 days at room temperature or freeze for 2 weeks.

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