In a medium saucepan, combine the marshmallow spread, canned pumpkin, light brown sugar, water, heavy whipping cream, pumpkin pie spice blend, vanilla extract, and fine sea salt. Use a whisk to blend these ingredients together thoroughly until smooth. This process should take about 3 to 5 minutes over medium heat until everything is well incorporated and a rich consistency begins to form.

Once combined, continue to heat the mixture over medium heat. Stir frequently to prevent any sticking to the bottom of the pan. After about 5 minutes, the syrup will start to bubble gently around the edges.

Allow the syrup to come to a gentle simmer, stirring occasionally for another 5-7 minutes. The mixture will thicken as the flavors meld together.

Once your syrup has reached the desired thickness, remove it from the heat. Let it cool in the saucepan for about 10-15 minutes.

Carefully pour the slightly cooled syrup into a clean glass jar or an airtight container using a funnel for ease. Make sure to seal it tightly.

To serve, drizzle it over your favorite coffee, hot chocolate, or pancakes.