In a large saucepan off the heat put the corn syrup, maple syrup and water. Stir.
Add the sugar and stir until sugar dissolves.
Put on stove, and bring to a boil, stirring frequently.
Reduce to a simmer, and simmer uncovered for about 15 minutes until it has reduced and thickened a bit. Stir frequently. Don't overcook or you will get a taffy.
Stir in walnuts, simmer another 5 minutes.
Ladle into quarter-litre (½ US pint) jars.
Leave 1 cm (¼ inch) headspace.
Debubble, adjust headspace.
Wipe jar rims.
Put lids on.
Process in a water bath or steam canner.
Process jars for 10 minutes; increase time as needed for your altitude.
Notes
Instead of walnuts, you can use pecans.Use a generous-sized saucepan in case of sudden boil-ups, to prevent wastage and sticky mess spills on stove. Using a wooden spoon can help prevent this.