Stir the milk, cream, sugar and vanilla/extract together.
If your filling/flavoring is something smooth like hot fudge, caramel, chocolate sauce, peanut butter or dry cake mix then mix it until it's dissolved. (sometimes you need to heat it before mixing it in, like the hot fudge or caramel sauce)
Start with a little and add more, since there is no eggs you can taste it as you mix and decide when it's enough.
Stir it well and make sure it's still cold, then run it through your ice cream machine according to the directions, about 30 mins
Stir in any fillings that are chunky, like chunks of chocolate, crushed cookies, sprinkles, nuts, marshmallows, toffee, etc... OR anything that you want to stir in like a ribbon, like peanut butter, hot fudge or marshmallow frosting...
Serve immediately for soft ice cream and freeze a few hours for firmer ice cream.