In two separate bowls (bowl must be microwave safe) break up semi sweet chocolate bars in one bowl and break up white chocolate bars in the other one. Melting one type of chocolate at a time, heat the chocolate in the microwave in 30 second increments, stirring the chocolate in between each round. Repeat until chocolate is completely melted & smooth. Do the same with white chocolate.
Line a baking sheet with parchment paper for the cookies to dry on.
Using a fork or a chocolate dipping tool (if your fancy) dip Oreo cookies into the chocolate, completely covering them. Lift cookie out of the chocolate with the fork and allow excess chocolate to drip off into the bowl. Place chocolate covered Oreo's on the baking sheet to "dry". Once all the Oreo's are covered in chocolate stick the baking sheet in the refrigerator for about 15 minutes so the chocolate will set and firm up completely. Store any leftover in an airtight container.