Melt the chocolate on top of a double boiler. (if no double boiler, heat some water on a saucepan, not boiling, and use a mixing bowl that can withstand heat. place the mixing bowl on top of the hot water and, using a whisk, stir the chocolate until melted. ).
In a small saucepan, mix the espresso and heavy cream and boil. Once boiled,whisk it into the chocolate.
Before you put any of the chocolate on the mold, you must line with plastic wrap so you can take the terrine out when ready. To do this, cut of as much plastic wrap as you think you need. Pour a little oil on one side of the wrap and with a pastry brush, spread it until the whole side is oiled. Place the wrap, oil side down, on your mold. Make sure there's some wrap hanging down on the side to make sure you can pull it out of mold later.
Place half the chocolate mixture into your mold and place in freezer until solid, 20-30 minutes.
Once the chocolate is solid, place as many raspberries as you'd like to cover the solid chocolate. Cover with remaining chocolate mixture (if that mixture has also become solid, just place on top of double boiler again. ).
Freeze until solid. Once you are getting ready to serve, place some parchment or wax paper on a plate. Pull the plastic wrap out carefully ( run some hot water outside the mold if it helps to loosen it) place the terrine on top of your plate, getting rid of the wrap. Serve with a few fresh raspberries on top.