Preheat oven to 350F. Grease three 8-inch round cake pans, and line the bottoms with parchment paper.
In a large bowl, sift the flour, baking powder, baking soda and salt.
In another bowl, whisk sour cream, lemon zest, juice and vanilla.
Beat butter and sugar together on medium speed in a bowl of a standing mixer until light and fluffy. Beat in eggs, one at a time, until blended.
Reduce the speed to low and beat in 1/3 of the flour mixture, followed by half of the sour cream mixture. Repeat with another 1/3 of the flour mixture and the remaining sour cream mixture. Beat in the remaining flour mixture until just incorporated.
Divide batter evenly among prepared cake pans. Transfer pans to oven and bake for 18 to 20 minutes or until wooden pick inserted in cake comes out clean. Cool in pan on wire rack for about 10 minutes before inverting on rack. Let cool completely.
Beat heavy cream with powdered sugar until the mixture holds stiff peaks. Place into the fridge to chill.
To assemble, place one cake layer on the serving late and spread with half of the strawberry jam. Gently spread a layer of whipped cream on top, and scatter half of the chopped strawberries. Top with another cake layer and repeat the jam, whipped cream and strawberries. Top with the final cake layer.
Frost the top and sides of the cake with the remaining whipped cream. Press white chocolate around the sides of cake and place whole strawberries on top. Refrigerate until ready to serve.