Add the prosecco and strawberry jam to a mixing bowl. Whisk to combine. Set aside.

Place 28 ladyfingers into a large pan so they are laying flat. Pour the champagne mix on top. Set aside. They should soak for at least 10 minutes. About the time it will take you to slice the strawberries and prepare the mascarpone filling.

Add the heavy whipping cream, powdered sugar, and vanilla to a large mixing bowl. Using a hand mixer, mix until soft peaks form, about 3-4 minutes. Add the mascarpone and mix until stiff peaks form about 2 minutes. Set Aside.

Place the strawberries into a bowl with the lemon juice and toss to combine.

To assemble, spread ⅓ of the whipped cream mascarpone mixture into the bottom of a 9x9-inch pan. Next, lay down 12-14 ladyfingers so they are laying flat and not overlapping. Spread another ⅓ of the cream mixture over the ladyfingers. Place half of the strawberries on top of the cream so they are laying flat. Continue with the next and final layers.

Cover with plastic wrap and refrigerate for at least 5 hours or overnight.