In a medium saucepan, whisk the marmalade, soy sauce and ¼ cup of water. Heat on medium high until simmering. Reduce heat to low and keep simmering.
½ cup orange marmalade, ¼ cup low sodium soy sauce
In a separate bowl, (I just use the measuring cup), whisk together the rest of the water (1 cup) and the corn starch.
1¼ cup water, 1 tbsp corn starch
Whisk a little of the marmalade mixture into the corn starch mixture and then whisk all of that mixture into the marmalade. Continue to whisk while simmering on low heat until thickened.
Notes
It stores well in an air tight container in the fridge for 3 to 4 days.