1 to 2 tablespoons Cointreau, or orange flavoured liqueur
In a saucepan whisk together the four eggs, four yolks, 3/4 cup sugar, salt and the lime juice. Cook over medium/low heat while stirring constantly until it thickens, about ten minutes. The key lime curd is done when it is as thick as pudding and coats the back of a spoon or spatula. Press through a fine mesh strainer and cool.
Whip the egg whites and remaining 1/4 cup of sugar until they reach stiff peaks. Add 1/3 of the whites to the chilled key lime curd and mix to lighten the texture of the curd. Gently fold the remaining whites in.
Whip the heavy cream with the vanilla extract until stiff peaks. Fold the whipped cream gently into the key lime mousse. Fold just until the cream is smoothly incorporated and refrigerate until ready to eat.
Combine the graham cracker crumbs, sugar and melted butter and set aside.
Mix the berries, sugar and liqueur in a bowl and let the berries sit for at least 30 minutes, so they release some of their juices.
To serve, fill the bottom of a mason jar with the key lime mousse, top with the strawberries and then sprinkle the graham cracker crumbs on top. Enjoy!