Blend the whole frozen strawberries with just enough milk from the recipe to get things moving smoothly.
In a separate wide bowl, add the sliced strawberries and sprinkle them with sugar. Let them sit for 30–40 minutes to release their juices, then mash them using a wire masher.
Next, in the same bowl, combine the mashed strawberries with the strawberry puree, remaining milk, heavy cream, and vanilla extract. Stir everything together until well mixed, then pour the mixture into the ice cream maker’s freezer bowl. Churn according to your machine’s directions.
After about 25 minutes, check the consistency — it should resemble soft serve when it's ready. Transfer the ice cream to a loaf pan or airtight container, pressing plastic wrap directly onto the surface to help prevent ice crystals from forming.