Place the chocolate in a heatproof bowl and microwave in increments of 30-40 seconds until the chocolate is melted. Stir until smooth. Set aside to cool while you whip the cream. (see recipe notes for alternative methods)
Whip cream until soft peaks form. This will take about 8-10 minutes in a stand mixer. Do not over-whip the cream, or you'll end up with butter.
Use a spatula to gently fold the chocolate through the whipped cream until it's combined.
Fill your piping bag with the chocolate mousse and pipe into the tart shells. Alternatively, you can use a spoon.
Refrigerate the tarts for 1-2 hours until the mousse is set.
Serve these tarts on a platter. Top with fresh fruit, shaved chocolate or coconut.
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Notes
Double Boiler Method: If you don’t have a microwave, melt the chocolate using a double boiler. Fill a saucepan halfway with water and bring it to a gentle simmer over medium heat. Place the chocolate in a heatproof bowl that fits snugly over the saucepan without touching the water. Stir until smooth, making sure no water gets into the chocolate.Filling theTarts: You can spoon the mousse into the tarts, but using a piping bag will make the tarts look neater and more uniform. To pipe, use a medium-sized round piping tip and fill your bag with the mousse. Start in the middle of the tart, gently squeeze until the tart is full. If you pipe around in circles, the tarts look funny. Make Ahead of Time: To make ahead of time, make the chocolate mousse filling, then store it in an airtight container. If transporting to somewhere else, I find it easier to transport the tarts and filling separately so they don't get squashed, then assemble them when I get to my destination.