I toast the walnuts then chop them until they're fairly small. Go heavy on the lemon zest! A medium zuke usually yields 2C grated, so I double the recipe and make 36 mini muffins. 13 - 14 minutes is plenty of time to cook these and I fully rotate the trays (I have 6 muffin trays so put 2 on a quarter sheet pan) halfway through baking. I don't sugar the tops because I think there's enough sugar already between the sugar and the raisins.
KA suggests: If you don't have Apple Pie Spice, use 1 teaspoon cinnamon, 1/2 teaspoon nutmeg, and 1/2 teaspoon allspice in the filling. I don't think that's enough cinnamon in the ratio, but it's still tasty.
Roll into balls prior to refrigeration; vinyl gloves are a great help here since the dough is sticky. Can be kept in fridge in any container, covered, for up to 2 days prior to cooking so having the balls ready to go saves on space. Put the sheet pan with parchment in the fridge to chill while oven preheats.