Combine milk and heavy cream in a bowl and mix together.
Add sugar substitute and vanilla extract. Stir well until dissolved.
Transfer the mixture to a chilled bowl and place in the freezer for 1 hour.
Take it out and stir with a fork, then return to the freezer.
Repeat stirring every hour for a total of 3 to 4 times to keep the texture smooth.
When fully frozen, scoop the ice cream into bowls and serve.