Preheat oven to 220 C / Gas 7. Lightly grease a 30x20cm or similar sized roasting tin.
Place walnuts, pistachios, caster sugar and ground cinnamon into food processor. Process until well combined and coarsely ground. Spoon mixture into a bowl. Set aside.
Have the pastry ready with a damp towel covering the sheets between use. Using a pastry brush each layer of pastry with butter. Fold 1 sheet to form the first two layers.
Form four layers of buttered filo then sprinkle with nut mix. Continue layering filo sheets, brushing with butter after each addition.
Brush top filo layer with butter and tuck down edges. Using a sharp knife score pastry into 5cm squares. Bake in preheated oven for 10-15 minutes or until the top is golden.
To make the toffee, place sugar, honey, vinegar and cinnamon stick in a small saucepan over low heat. Gently heat until sugar has dissolved. While stirring, gently raise heat until mixture foams. Remove from heat and allow to cool slightly. Remove cinnamon stick.
To assemble, lightly grease enough muffin tins for 50 servings. Place one 5cm square of baklava into each muffin hole, then pour toffee mixture all over. Let set.
Store any leftovers in an airtight container for a few weeks.