Toss the chopped strawberries, vanilla and 4 tablespoons sugar in a bowl. Set aside until syrupy, about 30 minutes.
Trim off the tops of the whole strawberries. Cut the cake into 1/2-inch-thick slices, then use a 1 1/2-inch-round cookie cutter to cut out 24 rounds.
Beat the egg white, marshmallow cream, lemon juice, salt and the remaining 2 tablespoons sugar with a mixer on medium speed until stiff peaks form (the mixture may separate before coming together), about 5 minutes.
Dip one side of each cake round about halfway into the strawberry syrup and transfer to a baking sheet, syrup-side up. Spoon some of the chopped berries in the center. Top with a dollop of marshmallow cream.
Swirl the tip of each whole strawberry in the meringue. Press a strawberry, cut-side down, into the marshmallow cream on top of each cake. Toast the meringue with a kitchen torch or broil until golden, rotating as needed. Serve immediately.