• Preheat oven to 350 degrees Fahrenheit and line cupcake or muffin tins with 18 paper liners of your choice.
• Next, start preparing the cupcake batter by adding the butter and white sugar to the bowl of a stand mixer. Beat the ingredients together on medium-high speed for several minutes, until the mixture becomes light, fluffy and pale in colour.
• Beat in each of the 5 eggs, one at a time, on medium speed, stopping between each addition to scrape down the sides and the bottom of the bowl to make sure everything is incorporated evenly.
• Measure the flour, baking powder and sea salt into a separate bowl and set it aside.
• Measure out the milk and add the vanilla to it.
• Add the dry ingredients and wet ingredients alternately, starting and ending with the dry ingredients. Add the ingredients on the lowest speed and be careful not to over mix...only let the mixer run until the ingredients are just combined. Add the last addition of dry ingredients by hand with a rubber spatula just to prevent over mixing, which leads to a tough and dense crumb.
• Divide the batter evenly between the 18 paper liners, filling each about 3/4 full. Measure out one teaspoon of strawberry jam onto the top of each well of batter. Using a butter knife, cut into the jam and swirl it around in the top half of the batter.
• Place pans in the oven and bake at 350 for 18-20 minutes. Remove pan from oven and wait 2 minutes, then remove the cupcakes from the pan and let them cool completely on a wire rack.
• While you're waiting for the cupcakes to cool you can begin to prepare the frosting.

For the Frosting:

• Chop 5 or 6 strawberries as finely as you can. You'll need to add 1/2 cup chopped fresh strawberries to the frosting, but once they've been chopped, add the strawberries to a strainer over a bowl to let the excess liquid drain out of them while you prepare the rest of the frosting.
• Add the butter and 4 cups of icing sugar to the bowl of your stand mixer, along with the milk. It's a good idea for the butter to be just slightly cooler than room temperature for this frosting because of the high water-content in the strawberries. Beat the butter, icing sugar and milk on high speed until you end up with a stiff buttercream frosting. You'll probably have to scrape down the sides of the bowl a few times to make sure everything is incorporated.
• Measure out 1/2 cup of the drained strawberries and add them to the stiff frosting. Beat them in on medium speed, scraping down the sides of the bowl to make sure everything is evenly incorporated.
• At this point, your frosting may be too soft to pipe, so add as much of the remaining 2 1/2 cups of icing sugar as you need to create a frosting that's of piping consistency (this means it will hold its shape when piped on top of a cupcake). Add the remaining icing sugar 1/2 cup at a time, and don't forget to add in the pinch of salt too (this tones down the sweetness of the frosting just a bit).
• If you're not happy with the colour of the frosting after adding the strawberries, simply stir in a touch of red food colouring (I don't always do this...the cupcakes pictured in this blog post are made without food colouring).
• Once the frosting is prepared and the cupcakes have cooled completely to room temperature, you can go ahead and frost the cupcakes however you like! Because this frosting is so fluffy and soft, I chose to pipe the frosting on each cupcake in a circular motion using a medium plain round tip. If you prefer the look of a star tip or any other style, go ahead and use that. It's up to you!
• Finish off each cupcake by nestling a fresh, ripe strawberry into the top of the frosting.