Prepare the ganache as above and pour it into a mixing bowl to cool. The bowl should be large enough to hold your mousse since this is where you will prepare it..
Chill the mixing bowl and the beaters you will use to whip the cream. Ten minutes the refrigerator should be fine. You can do this while you're waiting for the ganache to cool.
Bloom the gelatin in the cold water in a small, heat-proof bowl. Let it sit for five minutes until it forms a sponge
Microwave the the gelatin for 5-8 seconds until it melts into a clear liquid. Let it cool for 2 minutes. I must be liquid but not hot.
Whip the cream and sugar in the chiilled bowl until it just begins to thicken. It should still be lilquid, not soft peaks.
Stream. While the mixer is running on slow speed, drizzle the liquid gelatin directly into the cream. Avoid the beaters or the sides of the bowl.
Finish the whipped cream. Add the almond extract if using and whip the cream to soft peaks. Avoid stiff peaks since that will result in a grainy texture for the mousse.
Loosen the ganache. Now place one third of whipped cream in the bowl with the cooled ganache. Using a rubber spatula, gently fold the cream and ganache together to loosen the chocolate..
Finish the mousse. Fold the remaing whipped cream into the bowl with the ganache. Use sweeping motions, folding the mixture over itself and rotating the bowl as you repeat. Stop when chocolate streaks disappear and the air is still trapped inside.
Spoon or pipe the mousse into your serving dish. That could be a pre-baked pie shell, serving glasses for a parfait, or a cake mold.
Chill at least four hours to set.