Line a rimmed baking sheet with parchment paper and make sure the parchment lies flat.
Add the chopped chocolate and the 1/2 teaspoon oil, if using, to a microwave-safe bowl.
Microwave the chocolate for 30 seconds.
Remove the bowl and stir well.
Microwave for another 30 seconds.
Remove and stir again.
Continue heating in 30-second intervals, stirring every time, until about 90 percent of the chocolate is melted.
Stop heating and stir until the chocolate is completely smooth.
Pour the melted chocolate onto the prepared baking sheet.
Use a spatula to spread the chocolate into an even layer about 1/4 inch thick.
While the chocolate is still warm, sprinkle the 1/4 cup of toppings evenly over the surface.
Spread the toppings out so they are not concentrated in the center.
Gently press the toppings into the chocolate with your fingertips or the back of the spatula.
Transfer the baking sheet to the refrigerator.
Chill for 20 to 30 minutes, or until the chocolate is completely set.
Lift the parchment paper and place the chocolate on a cutting board.
Break the bark into pieces by hand for a rustic look or use a sharp knife for cleaner edges.
Store the chocolate bark in an airtight container at room temperature for up to 5 days.
Store in the refrigerator for up to 2 weeks if needed.