Line a baking sheet with parchment paper or a silicone mat, ensuring it lies completely flat without wrinkles.
Melt the chopped dark chocolate in a double boiler or microwave in 30-second bursts, stirring between each interval until 90% melted. Remove from heat and stir until completely smooth.
Stir in the cooled espresso until fully incorporated and the mixture appears glossy and unified, about 30 seconds of gentle stirring.
Pour the chocolate mixture onto the prepared baking sheet and use an offset spatula to spread it into a thin, even layer about 1/4 inch thick.
Immediately sprinkle the toffee bits and toasted almonds evenly over the surface, pressing them gently into the chocolate so they adhere.
Finish with a light sprinkle of flaky sea salt across the entire surface for flavor contrast.
Refrigerate for at least 2 hours until completely firm and set, or freeze for 30 minutes if you're in a hurry.
Break the bark into irregular shards by hand or cut into clean rectangles with a sharp knife. Store in an airtight container with parchment between layers.
