2 tsp butter
1/2 Cup sugar
2 Tbsp Traditional Balsamic Vinegar
1/2 tsp Kosher Salt
1-1/2 tsp Dried Rosemary, roughly chopped
2 Cups walnut halves or pieces
Preheat oven to 350˚F. Line a rimmed baking sheet with foil, and spray the foil with a light coating of cooking spray. Rub the foil with a paper towel to spread the oil and cover the surface evenly. Spray lightly again. Set aside.
Place an (approximately) 18-inch piece of parchment paper on a heat-proof work surface (a marble board used for rolling pastry dough is ideal if you’ve got one).
Add butter to a large non-stick pan, and melt over medium heat. Add the sugar, balsamic vinegar and salt. Continue to cook, stirring continuously until the sugar is completely dissolved. This should take about 3-4 minutes. Add walnuts and chopped rosemary to the butter mixture, and stir gently with a heat-proof spatula so that the walnuts are well-coated with the sugar mixture.
Turn out the seasoned buttered walnuts onto the prepared sheet pan, and place in the preheated oven. Bake nuts for about 15 minutes, removing from oven and gently stirring every five minutes until nuts are deep golden brown.
Remove baking sheet from oven and immediately turn contents out onto prepared parchment paper. Working quickly, separate the coated, seasoned nuts with two forks.
Sprinkle generously with coarse flaky sea salt as the nuts cool. Allow to cool completely before serving, or before storing in an airtight container.