Preheat oven to 350 degrees F.
Butter and flour two 8 inch cake pans.
Cream the butter and sugar until light and fluffy, about 5 minutes. This is easiest done in a stand mixer with a paddle. Scrape down the sides of the bowl.
Add the eggs, one at a time, beating after each addition to incorporate.
In a large bowl, whisk together the flour, baking powder, and salt.
In another bowl, combine the milk, vanilla extract and vanilla seeds.
With mixer on low, alternate adding the flour mixture and milk mixture, starting and ending with the flour mixture.
Shut off the mixer, scrape down the sides of the bowl, and ensure everything is well-combined.
Evenly divide the batter between the two pans.
Bake 40 minutes until a toothpick or skewer comes out clean.
Let cakes cool for 15 minutes, then remove and set aside to finish cooling on a wire rack.
To make frosting, cream the butter about 30 seconds with a mixer.
Add the sugar and mix for another 5-7 minutes, until light and fluffy. Scrape the sides of the bowl to make sure everything is incorporated.
In a small saucepan, add ¼ cup milk, the vanilla and flour. Whisk together and then turn to medium heat.
Add the rest of the milk, whisking slowly until mixture starts to thicken. Once it starts to thicken, remove from heat, and continue whisking for another minute. If you have lumps, strain the mixture. Let cool to room temperature.
Once mixture has cooled, add to the butter/sugar mixture and beat about 4-5 minutes.
Frost the cake, leaving a little icing aside to color. Color the remaining frosting and then pipe onto the cake to decorate.
Serve with sliced strawberries and blueberries.