Prepare an 8x8 pan by lining it with aluminum foil and spraying the foil with nonstick cooking spray.
Place the peanut butter, baking soda and vanilla in a small bowl and set aside for now.
Place the sugar and water in a medium saucepan over medium high heat. Stir constantly until the sugar dissolves. Bring the sugar syrup to a boil, and stir in the corn syrup. Insert a candy thermometer.
Continue to cook syrup, boiling it without stirring, until it reaches 300 degrees on the thermometer. Watch the pan carefully, as the sugar can quickly rise in temperature and burn at such high heat.
Once it candy reaches 300 degrees, immediately remove it from heat. Quickly stir in the peanut butter, baking soda, and vanilla and stir until it is smooth.
Pour the candy into the prepared 8x8 pan, and allow it to sit for about two minutes. While it is still warm and pliant, take a large knife and score it into ten pieces:make a cut down the center, then cut each half into five pieces, for a total of 10 candy bars. Allow the candy to set at room temperature, for at least 4 hours or overnight.
Once the peanut candy is completely set and firm, prepare the chocolate for dipping. Place the chocolate candy coating in a large microwave safe bowl and microwave it until melted, stirring after every minute to prevent overheating. Stir the melted chocolate and allow it to sit at room temperature for about 5 minutes to cool it slightly. Line a baking sheet with foil and set it nearby.
While the chocolate is cooling, carefully cut or break the peanut candy into bars along the scored lines.
Using two forks or dipping tools, submerge one bar in the melted chocolate. Remove the bar from the chocolate, allowing the excess chocolate to drip back down in the bowl. Place the dipped bar on the foil lined sheet. Repeat the dipping with remaining bars and chocolate, and place the bars in the refrigerator for 10 minutes to set the chocolate. Once set, the bars can be served immediately. Store remaining bars in an airtight container at room temperature for up to a week.