Preheat oven to 375 degrees F. Line baking sheets with parchment paper (or line with silpats or leave sheets ungreased).
In a large mixing bowl, beat together peanut butter, butter, and brown sugar with electric mixer on medium speed until well combined. Beat in egg and vanilla.
In a separate bowl, combine flour, baking soda, and salt. Beat into cookie dough until combined.
Using a 2-teaspoon scoop, scoop dough and drop onto prepared baking sheet(s). If desired, use a fork to form a criss-cross pattern on top of cookies.
Bake cookies at 375 degrees F for about 7-9 minutes or until just lightly browned underneath being careful not to overbake. Cool completely on wire racks.
Place chocolate chips in small bowl. Place heavy cream in microwave safe bowl. Microwave cream on high for 30 second intervals until hot and bubbly. Pour over chocolate chips. Stir until chocolate has melted and mixture is smooth. Cool slightly.
Spread chocolate filling on bottom of each cookie, sprinkle Pop Rocks on top of chocolate, then combine two cookies to form sandwich. Serve immediately or store in air-tight container.
SNAPPY TIPS: The longer the Pop Rocks sit in the chocolate and get soft the less they will "pop" so serve cookies immediately or instead of putting Pop Rocks inside of cookie put them around the edges of the cookie/chocolate just before serving. Instead of forming sandwiches, you could also frost cookies with the chocolate and sprinkle Pop Rocks on top.SNAPPY SUBSTITUTIONS: Instead of dark chocolate chips, you can use any variety of chocolate chips such as semi-sweet, milk chocolate, or bittersweet. You can also use any flavor of Pop Rocks such as strawberry.
Keywords: chocolate and peanut butter recipe, homemade peanut butter cookie