Combine the Nutella and about half of the cream in an 8 cup glass measuring cup or large bowl. Heat & whisk in the microwave for about a minute, or until the Nutella melts and the mixture is smooth.
Add the rest of the cream, milk, sugar, vanilla, and salt. Cover and chill for at least 3-4 hours or until very cold.
Churn base in an ice cream maker according to the manufacturer's instructions.
While the ice cream churns, prepare the swirl. Combine the 1/2 cup Nutella and tablespoon of coconut oil in a small glass bowl. Heat and stir in the microwave for 30-60 seconds, or until smooth. Chill until the ice cream is ready.
In a freezer-safe container, layer a third of the ice cream mixture and a third of the nutella mixture. Repeat two times, then swirl with a butter knife.
Freeze the ice cream for 3-4 hours, or until firm enough to scoop.
Notes
Makes about 1 1/2 quarts of ice cream.
If you don't have an ice cream maker, you can melt the Nutella in the milk, then add the sugar, vanilla, and salt. Chill it for 3-4 hours. Then beat the cream with a hand mixer until stiff peaks form, and fold it into the chocolate mixture. Pour into an airtight container or loaf pan covered with plastic wrap. Freeze for 8 hours or overnight.