Preheat oven to 350* and grease baking sheets, or use parchment or silpat.

In an electric mixer, fitted with a paddle attachment, beat together peanut butter and sugar until combined well.

Add beaten egg and baking soda until combined well.

Roll level teaspoons of dough into balls. Arrange 1" apart on baking sheets and with the back of a fork, press balls down making a cross-hatch pattern.

Bake cookies in a batches in the middle of the oven until puffed and golden, about 10 minutes

Cool cookies on baking sheet 2 minutes, and then transfer to racks to cool completely.

Store in an airtight container for 1 week. Makes about 70.