Special equipment: a large pastry bag fitted with a medium open tip (Ateco 806); a candy thermometer; a large pastry bag fitted with a large open tip
For the sponge: Preheat the oven to 350 degrees F. Trace two 8-inch circles on 2 baking sheet-sized pieces of parchment with a marker. Flip them upside down onto 2 baking sheets. Set aside.
Into the bowl of a stand mixer fitted with the whisk attachment, add the egg yolks and whisk on high until lightened in color. Slowly add the vanilla and 1/4 cup of the granulated sugar and continue whisking until the mixture triples in volume and ribbons when the whisk is lifted from the batter, leaving a trail that takes a few seconds to dissolve back into the mixture, about 5 minutes. Sift the flour over the mixture and fold in to incorporate until there are no pockets of flour left.
Transfer the egg yolk mixture to a small bowl and clean the mixing bowl and whisk very well. Add the egg whites to the bowl and mix on high until just foamy. Add the salt and then slowly add the remaining 3/4 cup granulated sugar, whisking on high until the meringue holds stiff, glossy peaks, 3 to 5 minutes.
Transfer a scant cup of the meringue to the egg yolk mixture and fold to combine and lighten. Add the remaining whites to the egg yolk mixture and gently fold into the batter until no white streaks remain. Transfer the batter to a large pastry bag fitted with a medium open tip (Ateco 806) and pipe 4 circles onto the parchment using the traced circles as guides, starting from the middle and spiraling out. Sift an even layer of confectioners' sugar over the batter.
Bake until the layers are gold brown and springy, 20 to 25 minutes. Let cool completely, then trim the layers using an 8-inch cake pan as a guide and a sharp knife to make the layers perfectly round.
For the filling: Whisk together the granulated sugar and cornstarch in a small bowl to combine. In a heatsafe bowl, whisk together the yolks, Marsala, salt and sugar-cornstarch mixture to combine. Place the bowl over a saucepan of simmering water, making sure the water does not touch the bottom of the bowl (otherwise you could scorch the eggs). Heat, whisking constantly, until the sugar is completely dissolved, the mixture thickens to the point that it coats the back of a wooden spoon and a candy thermometer inserted in the center reads 170 degrees F, 5 to 10 minutes. Remove from the heat and allow to cool to room temperature.
Whip the cream in a bowl with a mixer to stiff peaks. Fold together the whipped cream and cooled egg yolk mixture (zabaglione). Transfer the cream filling to a pastry bag with a large open tip.
For the trifle: Place a sponge round in the bottom of a trifle dish. Using a pastry brush, brush a generous layer of the Coffee Simple Syrup onto the sponge layer. Slice half of the strawberries in half and place them cut-side out around the sides of the trifle dish. Then place a few whole strawberries in the center. Pipe an even layer of the cream filling over the layer and sift an even layer of cocoa powder on top of that. Top with another sponge round, brush with the coffee syrup and then top evenly with the raspberries. Pipe the cream filling on top of the raspberries and dust with cocoa powder. Top with another sponge, brush with coffee syrup and spread with a thin even layer of the cream filling. Dust with cocoa powder and decorate the top with more cream filling and the remaining berries. (Reserve the remaining sponge for another use.)
Put the coffee and sugar in a saucepan and heat, stirring, until the sugar is dissolved. Remove from the heat and let cool.