Place the milk in a small pot and bring it to a simmer over medium heat. Do not let it come to a boil. Turn off the heat and add the chamomile. Leave to steep until the milk is room temperature. Strain out the chamomile, but do not squeeze it or the milk might taste bitter. Discard the chamomile. Set the milk aside.
Preheat the oven to 350°F (175°C). Grease two 9 inch (23 cm) round cake pans.
Sift the flour, salt, baking powder and baking soda into a large bowl.
Using a stand mixer fitted with the paddle attachment, cream the butter with the sugar on high speed until light and fluffy, about 5 minutes. Add the eggs, egg whites and vanilla and mix well to combine, about 2 minutes. Scrape down the bottom and sides of the bowl as needed.
Alternate adding the flour mixture and the milk to the butter mixture, beginning and ending with the flour mixture. You want everything to be just mixed in for this batter. Scrape down the sides and bottom of the bowl as needed. Once the batter is combined, pour it into the prepared cake pans.
Bake until a skewer inserted into the centre of each cake comes out clean, 25 to 30 minutes. Place the cake pans on wire racks and let the cakes cool completely in the pans.