Preheat the oven to 350 degrees F. Butter two 8-inch round cake pans or a nonstick mini cheesecake pan.
Sift the flour, baking powder and salt in a medium bowl and set aside.In a large mixing bowl, cream the butter and sugar for 4-5 minutes. Add the vanilla extract. Add the eggs, one at a time, beating after each until incorporated. Using a rubber spatula, fold the flour mixture into the wet mixture until incorporated. Be careful not to over-stir or the cakes will be dense.Divide the batter between the two cake pans and smooth the tops with a spatula, or divide between the cavities of the mini cheesecake pan cups to the halfway point. Bake on the middle oven rack about 20 minutes for the cake pans or 12-15 minutes for the mini cheesecake pan or until a toothpick inserted into the center of a cake comes out clean or the top of the cake springs back when lightly pressed.Allow the cakes to sit for about 10 minutes before transferring them wire rack to cool completely.
To make the whipped cream filling: In a medium mixing bowl add the chilled heavy cream, powdered sugar and vanilla extract and beat until stiff peaks form. To make the alternative buttercream filling (especially suited for mini Victoria sponge cakes): Beat together the butter, powdered sugar and milk until smooth. If the buttercream is too stiff, add a tiny amount of milk until a spreadable consistency is reached. If it's too runny, add more powdered sugar. Spoon the buttercream into a piping bag with a medium or large round tip (optional for prettier decorating).
Place the two 8 inch cakes side by side. Generously spread a thick layer of strawberry or raspberry jam over the top of one of the cakes. Then top with the whipped cream. Place the second cake on top of the cream with the top facing up. Dust the cake with powdered sugar.
For mini Victoria sponge cakes: Once the cakes have cooled completely, slice them in half. Spread or pipe the buttercream onto the bottom half. Then spoon some jam on top of the buttercream. Place the top half of the cake on the bottom half. Dust the tops of the mini cakes with powdered sugar.
Serve immediately or store in an airtight container in the fridge. Will keep for 3 days.