Set a medium bowl in a large bowl of ice water. In a small saucepan, combine the cream, milk, sugar and salt and bring to a simmer, stirring to dissolve the sugar completely. Pour the ice cream base into the medium bowl and let cool completely, stirring occasionally. Refrigerate until very cold, at least 1 hour or overnight.
Pour the base into an ice cream maker with flavorings, if using, and freeze according to the manufacturer's instructions. Transfer the ice cream to a plastic container, cover and freeze until firm, at least 3 hours.
Add flavorings to the ice cream maker at the beginning of the freezing cycle. Chocolate-Toffee: 1 cup broken chocolate-and-toffee-covered saltines or pretzels Blackberry-Sage: 3/4 cup blackberry preserves mixed with 1 tablespoon minced fresh sage Salted Caramel: 3/4 cup pourable salted- caramel sauce Strawberry-Jalapeño:1 cup strawberries macerated in 3 tablespoons sugar with 1 teaspoon minced jalapeño