Make Berry Sauce: Bring all sauce ingredients just to a boil in a 1 1/2 to 2 quart heavy saucepan over high heat, stirring occasionally, then reduce heat and simmer, uncovered, stirring occasionally, 15 minutes.
Transfer to a shallow bowl and cool to romm temperature stirring occasionally, about 30 minutes.
Chill, covered, until cold about two hours.
Make Almond Layers:
Put oven racks in upper and lower thirds of oven and preheat to 350°F.
Butter cake pans and line bottom of each with a round of parchment or was paper, then butter paper.
Pulse almonds with 1/4 cup sugar in a food processor until finely ground.
Beat together eggs and remaining 1 1/4 cups sugar in a large bowl with an electric mixer at high speed until pale, fluffy, and tripled in volume, about 6-8 minutes.
Beat in vanilla and salt until combined well.
Stir together ground almonds and melted butter (1 1/4 sticks).
Fold one third of egg mixture into almond mixture to lighten, then fold in remainder, gently but thoroughly.
Divide batter among pans (batter should be about 1/2 inch deep).
Put 2 pans in lower third of oven and 1 pan in upper third (do not put directly above lower pans).
Bake, switching position of pans (from lower to upper and vice versa) halfway through baking, until a golden crust forms on top and cake begins to pull away from sides of pans ( cake will rise, them collapse slightly) 18 to 25 minutes total.
Cool in pans on racks 10 minutes, then run a small knife around edge of each pan and carefully invert onto racks.
Cool completely about 15 minutes.
Carefully peel off parchment.
Make Mascarpone Cream.
Stir together all mascarpone cream ingredients with a rubber spatula until smooth.
Center 1 almond layer on cake plate.
Spoon 1/2 cup berry sauce onto center of layer. Spread evenly, leaving a 1/2 inch border around edge of cake.
Spoon 3/4 cup mascarpone cream on top of berry sauce layer and smooth top (berry sauce will swirl into mascarpone cream).
Repeat procedure with remaining almond layers, berry sauce, and mascarpone cream, ending with mascarpone cream ( for a total of three layers).
Chill cake while making frosting.
Beat cream with sugar, vanilla, and salt in a large bowl using an electric mixer with cleaned beater at high speed until it just hold stiff peaks.
Frost cake with whipped cream smoothing top and sides (there will be generous amount) then chill, uncovered, 1 hour.
Just before serving, sift cocoa powder over top of cake using a sieve.
Cook's Notes: Almond layer can be made ahead and cooled completely, then wrapped well in plastic wrap and chilled 3 days or frozen up to 1 month.
Frosted cake can be made 1 day ahead (without cocoa powder) and chilled covered loosely with plastic wrap.