Heat the heavy cream in a 2-quart heavy-bottomed saucepan until bubbles begin to form around the edge of the pan. Make sure you chopped the chocolate as finely as possible to allow it to melt quickly and easily. Place the chopped chocolate in a medium-size mixing bowl. Make a ganache by pouring about 1/2 of the hot cream over the chocolate and letting it sit for 30 seconds to melt the chocolate. Then, slowly whisk until smooth and homogenous. Do not add all of the hot cream to the cold chocolate at once. The shock of the temperature extremes will cause the fat in the chocolate to separate. As the chocolate melts, you will see some elasticity if there is no fat separation. This means the chocolate still has an emulsion; the fat molecules are still holding together. If the ganache separates, it loses its elasticity, collapses, and becomes very liquid. I use a hand-held immersion blender to ensure a smooth ganache and to keep the emulsion of the chocolate. Add the remaining cream gradually and mix until all of the hot cream is incorporated and the ganache is smooth and homogenous.
If the ganache separates, it is very easy to fix. Simply add a small amount of cold cream and whisk well. This will bring the ganache back together. The ganache should be thick, shiny, and smooth. Add the desired flavoring and mix until fully incorporated. Pour the ganache onto a plastic wrap-covered baking sheet and spread evenly with a rubber spatula. Cover the ganache with plastic wrap and allow it to cool for at least 4 hours at room temperature. I usually make the ganache at the end of the day and let it cool overnight. As it cools, it will thicken and set.
Use a ladle to fill the mold with white chocolate. When it is full, empty it into the bowl of chocolate. The inside of the mold should be evenly coated with chocolate. Wipe the edge of the mold clean on the side of the bowl and place it upside down on a wire rack placed over a baking sheet. Once the chocolate starts to harden, about 5 minutes, scrape the edge clean with a paring knife. When the chocolate sets, it shrinks or retracts from the sides of the mold. A clean edge will keep it from sticking and cracking as it shrinks. You can place the mold in the refrigerator for several minutes to help the chocolate to harden.
Use a spatula to spread some of the cooled ganache into the chocolate mold. Fill it just short of the top so there will be room to close the chocolates. When finished, use a spatula to spread tempered white chocolate over the ganache. Allow this to set. When the chocolate has set completely, unmold the chocolates.
Tip: If you have extra ganche, you can make truffles. Let the ganache cool until it is the consistency of toothpaste. Then roll it into balls. Use a chocolate dipping fork to dip the ganche balls in tempered chocolate until completely covered. Set the dipped truffles on a parchment paper lined sheet pan until set.