How to Make It
Combine the flour, eggs, milk, the 3 tablespoons of olive oil and a pinch of salt in a food processor and blend until smooth. Transfer the batter to a pitcher and let rest at room temperature for about 30 minutes.
Lightly oil a 7- or 8-inch nonstick skillet or crêpe pan and set it over moderately high heat. Pour in 3 tablespoons of the batter and quickly tilt the skillet in a circular motion to spread the batter evenly over the bottom. Cook the crespelle for about 45 seconds on 1 side, then flip it and cook for about 20 seconds on the other side. Continue making the crespelle, stacking them as you go. Add more olive oil to the pan as needed.
Preheat the oven to 425°. Set a large skillet over high heat. Add the spinach and cook, stirring, until just wilted. Transfer the spinach to a colander; let cool and squeeze out as much water as possible. Chop the spinach and transfer it to a bowl. Beat in 1/2 cup of the Parmigiano-Reggiano, the ricotta, egg, nutmeg and a pinch each of salt and pepper.
In a small nonreactive saucepan, bring the cream and butter to a boil. Add the lemon juice, lemon zest and thyme and cook over moderate heat, stirring occasionally, until slightly reduced and beginning to thicken, about 5 minutes. Remove the pan from the heat and stir in 1/2 cup more of the Parmigiano-Reggiano. Spread a thin layer of the sauce in the bottom of a 13-by-9-inch (3-quart) baking dish.
Spread 12 of the crespelle with a thin layer of the spinach filling. Loosely roll up the crespelle and place them, seam side down, in the baking dish. Pour the remaining sauce over the top and sprinkle with the remaining 2 tablespoons of Parmigiano-Reggiano. Bake for 15 to 20 minutes, or until lightly browned and bubbling. Serve immediately.