Combine the chocolate and 1 c. sugar in a large saucepan.
Add the half & half. Turn on medium heat, and stir occasionally.
Set the raspberries (which should be partially thawed) in a strainer over a bowl. Mash them a little to strain.
Mix the egg yolks and remaining 1/4 c. sugar in a glass bowl. Whisk until thick and light yellow. Set it aside.
Continue cooking the sugar, half-and-half, and chocolate mixture until it begins to steam lightly.
Temper the egg yolk mixture. While whisking the egg mixture, pour a small amount of the hot chocolate mixture into the eggs. Once the egg mixture is warmed, pour it back into the pot of chocolate mix.
Continue to cook this mixture over medium until it thickens. It is done when it can coat the back of a wooden spoon.
Pour strained raspberries into ice cream mixture.
Cool mixture by either putting in fridge overnight or putting the pan in a sink full of cold water for about 30 - 60 minutes. When cooled it should be no warmer than room temperature, but ideally around 40.
Once cool, pour it into an ice cream maker and freeze according to manufacturer's directions, typically 20 - 30 minutes for an electric machine.
Serve immediately (it will be like soft serve) or transfer to glass containers to freeze for several hours to be harder, like "real" ice cream.