Position a rack in the middle of the oven and preheat to 350°F. Rub a 9 1/2-inch fluted tart pan with olive oil.
Sift the dry ingredients into a large bowl, pouring back into the bowl any bits of grain or other ingredients that may remain in the sifter, and set aside.
In a large bowl, whisk the eggs thoroughly. Add the olive oil, milk, and rosemary and whisk again. Using a spatula, fold the wet ingredients into the dry ingredients, gently mixing until just combined. Stir in the chocolate. Pour the batter into the pan, spreading it evenly and smoothing the top.
Bake for about 40 minutes, or until the top is domed, golden brown, and darker around the edges, and a skewer inserted inserted into the center comes out clean. The cake can be eaten warm or cool from the pan, or cooled, wrapped tightly in plastic, and kept for up to 2 days.