Heat oven to 350ºF. Beat peanut butter, sugar, eggs and baking soda in large bowl with electric mixer 2 minutes or until smooth and blended. Stir in chopped peanuts.
Drop level tablespoonfuls 2 inches apart, flat side down, onto ungreased baking sheets. Bake, one sheet at a time, 10 minutes or until cookies are puffed and slightly golden. Cool 5 minutes on baking sheet; remove to wire racks to cool completely.
Ganache: Microwave cream in glass bowl on high 1 minute or until it just begins to simmer. Add chocolate chips; let stand 2 minutes. Stir until chocolate is melted and smooth; spread over half of cookie top and sprinkle with chopped peanuts. If ganache begins to firm up, microwave a few seconds at a time until easy to spread. Let set at room temperature.