Bring a pot of water to a boil and blanch the callaloo for 1 minute. Immediately transfer it to ice water to preserve the bright green color. Drain well and squeeze out excess moisture.

Add the callaloo and coconut milk to a blender. Blend until completely smooth.

Pour the blended mixture into a large bowl. Add the heavy cream, condensed milk, brown sugar, vanilla, nutmeg, cinnamon, and salt. Whisk until fully combined.

Cover and refrigerate for at least 4 hours or overnight.

Pour the chilled mixture into your ice cream maker and churn according to the manufacturer's instructions.

Transfer to a freezer-safe container and freeze for 3 to 4 hours before serving.