Start by prepping your ingredients. Toast the nuts and seeds in a dry skillet over medium heat until they are fragrant and golden, about 3-5 minutes. Allow to cool, then roughly chop the pistachios and hazelnuts.
Using a microplane, zest the thin-skinned orange, avoiding the bitter white pith. Then, slice the orange into thin chips. Optionally, dry these in the oven at 200°F for about 30 minutes to intensify the flavor.
In a double boiler or microwave, gently melt the dark chocolate until smooth and glossy. If using a microwave, heat in 30-second intervals, stirring until completely melted. Ensure the chocolate reaches about 88°F to 90°F for perfect tempering.
Once melted, remove the chocolate from heat. Stir in the orange zest, ground cardamom, and a pinch of flaky sea salt to infuse the chocolate with aromatic flavors.
Pour the melted chocolate onto the prepared baking sheet, spreading it into an even layer with a spatula, about 1/4 inch thick.
Sprinkle the toasted pistachios, hazelnuts, pumpkin seeds, chia seeds, sesame seeds, and orange chips evenly over the melted chocolate. Gently press them into the chocolate.
Sprinkle the remaining flaky sea salt over the top of the bark for a sweet-and-salty contrast.
Place the baking sheet in the refrigerator for about 1-2 hours, or until the chocolate is completely set. Once set, break the bark into pieces of your desired size.
