In a medium saucepan, whisk the egg yolks and ½ cup of sugar together well. Pour in 1 cup of milk and whisk again, then add another ½ cup of sugar, remaining milk, vanilla and salt. Set the pot over medium heat and stir frequently until the the mixture gets hot and thickens enough to lightly coat the back of a spoon. Do not let the custard mixture come to a boil or it will not stay smooth. Reduce the heat to medium low if needed.

Remove the hot creamy mixture from the heat, whisk in the cream and let it cool, then cover it with plastic wrap and place in the fridge until chilled, at least 1-2 hours.

Meanwhile, make the raspberry puree by placing the the remaining sugar (¼ cup) and the raspberries in a small food processor or the cup of an immersion blender and blend briefly, just until pureed. Don't overmix the raspberry sauce or you will break up the seeds and make the sauce granular. You can use the sauce as is, or you can strain it through a fine mesh sieve to remove the seeds. Place the finished raspberry puree in the fridge to chill.

Once the ice cream mixture is chilled, start your ice cream maker and pour it into the freezer bowl of the ice cream maker. (Follow manufacturer's directions for your particular model.)

Churn it until it is a creamy soft ice cream, this takes about 20-25 minutes. At this point you can decide to add the raspberry puree in and churn until it's fully mixed in or scoop the ice cream out into a large bowl and swirl the raspberry sauce through in ribbons.