Preheat your oven to 350°F (175°C).
Spread the walnuts and hazelnuts on a baking sheet and toast them in the oven for 8-10 minutes, or until they are lightly golden. Allow to cool.
In a large saucepan, combine the grape juice and sugar.
Heat over medium heat, stirring until the sugar is fully dissolved.
Bring the mixture to a boil, then reduce the heat and simmer for about 10 minutes.
In a separate bowl, mix the flour, cornstarch, cinnamon, nutmeg, and salt.
Gradually add the flour mixture to the grape juice mixture, whisking constantly to prevent lumps.
Continue to cook over medium heat, stirring constantly, until the mixture thickens to a pudding-like consistency, about 10-15 minutes.
Line a baking sheet with parchment paper or a silicone mat.
Dip the toasted nuts into the thickened grape juice mixture, making sure they are well coated.
Thread the nuts onto a string or skewer to form a chain. Allow excess coating to drip off.
Place the coated nuts on the prepared baking sheet.
Allow the Churchkhela to dry in a cool, dry place for 2-3 days. You can hang them or lay them flat on the baking sheet.
Once fully dried, cut the Churchkhela into pieces and serve.
Enjoy your meal!