Instructions

1. Prepare the parchment paper: Cut or tear 39 (10-inch or a little larger) square pieces of parchment paper. Line 2 large plates each with a sheet of parchment and set the rest aside.
2. Prepare the batter: Sift the flour, sugar, and salt into the bowl of a food processor fitted with the blade attachment or blender. (You can also use an electric hand mixer, immersion blender, or whisk and a large bowl.) Add the cream and eggs. Process or blend until thoroughly combined into a batter that is smooth, lump-free, and a bit frothy and bubbly on top, 20 to 25 seconds (or mix with a handheld tool for about 1 minute). If there are any lumps, pour the batter through a fine-mesh strainer into another bowl and discard the lumps.
3. Add the butter: Add the butter and mix until fully incorporated.
4. Chill the batter: Cover with plastic wrap, or if using a food processor or blender, transfer the mixture into a bowl and then cover. Refrigerate for at least 1 hour and up to 24 hours.
5. Heat the pan: Position a cooling rack near the stove. Heat a 7- or 8-inch nonstick crêpe pan or 9- to 10-inch nonstick skillet over medium-high heat. Brush the pan lightly with oil, just enough to coat the bottom. Heat until very hot, about 1 minute, and then place the pan on an unheated burner for a moment.
6. Cook the first crêpe: Using a 1/4-cup measuring cup or ladle, pour the batter into one spot on a bottom edge (but not side) of the pan. Immediately pick up the pan, tilt it, and swirl the batter around the entire perimeter and then across the whole bottom to completely coat it in as even and thin a layer as possible. Pour any excess batter back into the bowl. Place the pan back on the heat. Cook until the edges are lightly browned and the bottom has become a pale golden-brown, 45 seconds to 1 minute (peek by lifting an edge slightly with a spatula). Gently work the spatula under the crêpe and carefully flip it over, helping it with your fingertips if necessary. Cook the second side until it has a few brown speckles and there is no raw batter visible, 45 to 50 seconds. Pick up the pan and slide the crêpe onto 1 of the plates lined with parchment. Cover the crêpe with another sheet of parchment.
7. Cook the rest of the crêpes: Repeat the process with the remaining batter, stacking about 15 crêpes on each plate with parchment between each. Cover the top crêpe of each stack with parchment. If the batter thickens beyond the consistency of heavy cream as you cook, add a little more cream or half-and-half, 1 tablespoon at a time, and stir to combine before making more crêpes. Brush the pan with oil after 8 or 10 crêpes are made to ensure that they will be easy to turn and slide neatly out of the pan. You should have 32 to 34 crêpes when finished.
8. Wrap and chill the crêpes: Wrap the stacks, still on the plates, in plastic wrap and refrigerate for 30 to 45 minutes before assembling the cake. Meanwhile, prepare the filling.
9. Cream the butter and sugar: Place the butter in the bowl of a stand mixer fitted with a paddle attachment. (Alternatively, use an electric hand mixer and large bowl.) Beat on medium speed until soft and fluffy, about 2 minutes. Add the powdered sugar and beat on medium speed, scraping the bottom and sides of the bowl, until fully incorporated, about 2 minutes.
10. Add the flavorings: Add the vanilla and hazelnut liqueur if using, and beat on medium speed until combined. Add the Nutella and continue to beat on medium speed until fully combined and there are no streaks of Nutella or the butter-sugar mixture.
11. Add the cream: Add the cream and beat until the filling is lighter in color, very fluffy, and easy to spread, about 3 minutes.
12. Start to assemble and fill the crêpe cake: Remove the crêpes from the refrigerator and remove the plastic wrap. Take 1 crêpe from the pile (always keep the top crêpe covered with parchment as you assemble so that it doesn't dry out) and use kitchen shears to trim any untidy strands or uneven edges. Place the trimmed crêpe on a serving platter or plate. Using an offset spatula, gently spread 2 generous tablespoons of the filling evenly over the crêpe, leaving about a 1/2-inch border uncovered.
13. Layer the next 13 crêpes: Trim another crêpe as needed. Place it on top of the first and repeat with spreading on the filling. Repeat with 12 more crêpes. You will have some extra crêpes, so if one isn't the loveliest, set it aside and continue with the next crêpe. As the crêpes are stacked and each layer gets filled, the weight of them will gently push the filling out to the edges.
14. Layer the next 10 crêpes, leaving a smaller border: Stack and fill 10 more crêpes, leaving a 1/4-inch border uncovered on each one.
15. Layer the final 5 crêpes with no border: Stack and fill 5 more crêpes, spreading the filling all the way to the edges. Place the last pretty crêpe on top (the 30th), but do not cover it with filling.
16. Wrap and chill the cake: Wrap plastic wrap around the cake and under the serving plate to cover the entire thing. Refrigerate until firm and chilled, at least 45 minutes and up to 1 day.
17. Garnish and slice: Unwrap and garnish the top with powdered sugar and chocolate curls or shavings if desired. The cake is best sliced cold: warm a long heavy knife by running the blade under hot water and then drying it with a paper towel before cutting. The warm blade cuts through far better and gives very clean cuts with fewer smudges and drags. Warm and dry the blade between cuts.