Melt the white baking chips in the microwave in 20-second intervals, stirring in between until smooth.
Using a fork, place an Oreo in the melted white chocolate. Move the cookie around with the fork to ensure it is coated. Flip it to the other side and repeat. Pick the cookie up out of the chocolate with the fork and let it drip for a couple of seconds to remove excess chocolate. Set it on the parchment paper. Repeat with the remaining cookies.
Let the cookies set for 15 to 20 minutes or until the white chocolate has hardened.
Melt the dark chocolate chips in 20-second intervals, stirring in between until smooth.
Using a piping tool or spoon, drizzle the dark chocolate onto the white chocolate covered Oreos slowly to create lines.
Add the mini M&M's onto the lines before the chocolate dries to form the Christmas lights.
Notes
Use only the green and red M&M's for red and green lights, or use all of the colors for multicolored lights.
Store the cookies either at room temperature or in the refrigerator.
They can also be frozen for up to 2 months. Allow them to defrost in the refrigerator overnight.