2 cups (454 g) fresh ricotta (page 186), well drained
3/4 cup (150 g) granulated sugar
1 teaspoon pure vanilla extract
1 cup plus 2 tablespoons (270 ml) heavy cream
2 sheets silver grade gelatin
To make the dacquoise layers, preheat the oven to 350°F (177°C) with racks in the upper and lower thirds of the oven. Line two baking sheets with parchment paper. Using a 9-inch cake pan as a guide, draw a circle in pencil on each piece of parchment paper, then turn over the parchment paper so that the writing can be seen through the paper. Lightly oil the parchment paper inside and slightly beyond the two circles with safflower oil or another neutral-tasting oil.
Combine the hazelnuts and confectioners’ sugar in a food processor and process until the nuts are the texture of medium-fine cornmeal, scraping down the bowl as needed.
Beat the egg whites with the salt at medium speed in a stand mixer fitted with the whisk attachment until they form soft peaks. With the mixer running, add the granulated sugar in a few additions, then increase the speed to high and beat until peaks form that are firm but not at all dry. (Alternatively, use a handheld electric mixer.) Use a large spatula to fold in the hazelnuts in three additions, until they are fully incorporated.
Divide the dacquoise mixture equally between the two baking sheets, spreading it with a small offset spatula to fill the circles in an even layer all the way to the edges. Bake until the layers are dry to the touch and light golden all over, 25 to 30 minutes, rotating the pans top to bottom and front to back halfway through baking.
Transfer the layers on their parchment paper liners to a flat surface. The cakes will have expanded slightly: to ensure they will fit into the pan, trim all around the edges of the warm layers with a sharp paring knife, using a 9-inch cake pan as a guide. Slide the layers onto a wire rack to cool completely.
To prepare the filling, put the pears in a small nonstick skillet and add the sugar and lemon juice. Stir over high heat until the fruit is translucent, 8 to 10 minutes. Remove from the heat. Transfer the fruit to a small strainer placed over a bowl and set aside to cool.
To make the ricotta mousse, press the ricotta through an ultrafine-mesh strainer or splatter screen (see page 14) into a large bowl. Use a spatula to stir in the granulated sugar and vanilla until well mixed.
In a separate bowl, whip 1 cup of the cream using an electric mixer until firm peaks form. Use a large spatula to fold the whipped cream into the ricotta mixture; set aside.
Put the gelatin into a small bowl of cool water to completely submerge it; let stand for 5 minutes to soften. Heat the remaining 2 tablespoons of cream in a bowl in the microwave or in a small saucepan over medium heat until it simmers. Squeeze the water from the soaked gelatin and stir it into the hot cream until it dissolves completely. Stir 1/4 cup of the ricotta mixture into the dissolved gelatin, then use a large spatula to fold this mixture back into the ricotta until well mixed. Gently fold the cooled drained pears into the ricotta mousse. (Discard the pear syrup or reserve for another use.) Cover the mousse and refrigerate for 2 hours.
To assemble the cake, place a dacquoise round top side up in a 9-inch springform pan. Spread the ricotta-pear filling over the cake, leveling the top. Top with the second cake. Cover the pan tightly with plastic wrap and refrigerate until set, at least 4 hours or up to a day. (The assembled cake may be frozen in the pan for up to 1 month. Transfer to the refrigerator to thaw overnight, then let stand at room temperature for 1 hour before serving.)
To serve, release the outer ring from the pan and transfer the cake on its base to a serving platter, or use a large spatula to transfer the cake directly to the platter. Dust the cake generously with confectioners’ sugar and cut into wedges with a sharp serrated knife.