Add remaining 6 tablespoons butter, sugar and vanilla to large mixing bowl with dough ball. Mix on medium speed until creamy and well combined - about 1-2 minutes. Mix in egg and water until well combined. Reduce mixer speed to low and beat in dry ingredients and chocolate chips until just combined. Chill dough in refrigerator while you prepare the peanut butter balls.
Heat oven to 350 degrees F. Divide cookie dough into 12 balls. Flatten each ball, place a peanut butter ball into the center, and wrap dough around ball so that it's hidden. Divide the 12 cookie balls onto two cookie sheets. Bake 12-14 minutes, or until crisp and slightly crackled.