Preheat the oven to 190°C, fan 170°C, gas 5. 2 baking trays should be lined with foil. Chop the walnuts and combine with the olive oil, parsley, and lemon zest in a mixing bowl. Season and mix well.
Fill each date with the walnut stuffing and pinch closed with a teaspoon.
Wrap a piece of bacon around each date and secure with a cocktail stick. Brush with maple syrup and arrange on baking trays. Bake for 20 minutes, flipping halfway through, until the bacon is crisp. Allow to cool for 5 minutes before serving on a serving plate. Any residual herby filler should be strewn about.