1. In a food processor or blender, smoothly purée spinach, parsley, garlic, oil, and lemon peel.
2. With a mixer, beat cream cheese until fluffy, adding 1 egg at a time. Add potatoes and mix well.
3. Spread potato mixture in a shallow 3- to 3 1/2-quart casserole. With the tip of a knife, impress shallow stripes or a lattice in potatoes, and spoon spinach mixture into these depressions.
4. Cover casserole tightly. Bake in a 375° oven until hot in center, about 35 minutes. Uncover and sprinkle nuts onto potatoes; bake 10 minutes more.