With the rack in the middle position, preheat the oven to 350 degrees F (180 degrees C). Butter and line an 8-inch (20-cm) springform pan with parchment paper.
For the batter: In a bowl, combine the flour, baking powder and salt. Set aside.
In another bowl, cream the butter and granulated sugar with an electric mixer. Add the eggs, one at a time, beating until the mixture is very light and fluffy, about 2 minutes. On low speed, add the dry ingredients alternately with the milk and vanilla.
Pour the batter into the prepared pan. Bake until a toothpick inserted in the center of the cake comes out clean, about 1 hour. Let cool for 10 minutes. Unmold and cool completely on a wire rack.
For the coffee chantilly: In a large bowl, whisk the cream with the powdered sugar, coffee and vanilla extract until soft peaks form. Set aside.
For the strawberries: Toss the strawberries with the granulated sugar and vanilla seeds.
To assemble the cake, spread half of the coffee chantilly in the center of one slice of cake. Garnish with half of the sliced strawberries and half of the chopped walnuts. Layer with a second slice of cake and repeat with the remaining chantilly. Garnish with whole fresh strawberries and walnuts.