Line a large baking sheet with parchment paper or a silicone baking mat. Set aside.

Melt the semi-sweet chocolate. You can melt it in a double boiler or the microwave. If using the microwave: place the chopped chocolate in a medium heat-proof bowl. Melt in 20 second increments in the microwave, stopping and stirring after each increment until completely melted and smooth.

Melt the white chocolate following the same melting process in step 2.

Pour the melted semi-sweet chocolate onto the prepared baking sheet and spread out into a large rectangle (anywhere around 8×12 inches is great). Drizzle the white chocolate mixture on top. (If needed, I have a visual of this step in my Sweetheart Swirl Bark video.) Use a knife or a toothpick to swirl the layers together. Decorate the top of the bark with candies.

Allow the chocolate to completely set uncovered at room temperature or in the refrigerator, about 45 minutes. Once hardened, break into pieces as large or small as you want.

Store bark in an airtight container at room temperature in a cool, dry place for up to 1 week or in the refrigerator for up to 2 weeks.