If you want to temper the chocolate follow the next steps. If not, jump to the end.
Spread chocolate over baking sheet lined with the parchment paper. Use an offset spatula to spread chocolate to form a thin layer.
Spread white chocolate over set dark chocolate. Use an offset spatula to spread chocolate to form a thin layer.
Melt dark chocolate over a double boiler or in the microwave. Stir until smooth. Add espresso powder to melted chocolate.
Spread melted chocolate over baking sheet lined with parchment paper. Make sure to obtain an evenly thin layer of chocolate. Use an offset spatula to help you do that.
Place tray in the fridge to set.
Melt white chocolate over a double boiler or in the microwave.
Mix coffee beans with melted white chocolate.
Spread white chocolate over set dark chocolate. Use an offset spatula to spread the white chocolate in an even layer.
Let white chocolate set before cutting the bark into shards.