In a 2-quart saucepan, warm the milk over medium heat until small bubbles form around the edges. Remove from heat and add the tea and orange zest. Cover and steep for five minutes.
While the milk steeps, add the chocolate, butter, sugar, smoked salt, and vanilla extract to a blender. After five minutes, strain the warm milk into a measuring cup and press down on the solids with the back of a spatula to extract all the flavor. Measure the milk again to ensure you have 1 cup (8 oz) and add additional milk if necessary. Pour the warm milk into the blender and wait 15-30 seconds to melt the chocolate and then blend on high speed for 30 seconds. Add the eggs and blend on high for 60 seconds. Add the heavy cream and blend for 30 seconds more. The mousse should be smooth and glossy.
Pour the mousse into a prepared 9-inch tart or pie shell or divide between small jars. Loosely cover and refrigerate until set, about 2-3 hours.
Just before serving, make the lavender-mascarpone whipped cream. In a small bowl, add the sugar and dried lavender buds. Gently rub together with your fingers until the sugar is fragrant.
In a cold metal bowl, stir together the mascarpone cheese, heavy cream, lavender sugar, and vanilla. Whip until soft peaks form.
Top the chilled mousse with the lavender-mascarpone whipped cream and sprinkle with more smoked sea salt, chopped dark chocolate, and lavender buds.