Put the semisweet chocolate in a large bowl and place in the microwave. Microwave on high for 1 minute, give the chocolate a stir, then microwave for another 30 seconds until completely melted. Set aside.
In clean bowl, beat the egg whites with an electric mixer at high speed until it holds medium peaks. Set aside.
In a chilled clean bowl, beat the cream with an electric mixer at high speed until it holds medium peaks.
Mix the yolks and tequila into the melted chocolate. Fold in 1/3 of the egg whites first to lighten the mixture, add the remaining 2/3 of the egg whites and fold gently to keep the air in the beaten egg whites. Add the whipped cream and fold in gently, taking care not to over mix.
Spoon the mousse into 4 martini glasses. Using a vegetable peeler, shave chocolate on top of the mousse. Garnish with mint. Chill for at least 1 hour or up to a day ahead.
*RAW EGG WARNING
Food Network Kitchens suggest caution in consuming raw and lightly-cooked eggs due to the slight risk of Salmonella or other food-borne illness. To reduce this risk, we recommend you use only fresh, properly-refrigerated, clean, grade A or AA eggs with intact shells, and avoid contact between the yolks or whites and the shell.