Preheat oven to 350 degrees F. Butter and flour a 9-inch baking pan.
Place oats in a bowl, pour the boiling water over and let soak for 30 minutes. Drain well.
Sift together the flour, baking soda, cinnamon, nutmeg and salt on waxed paper. Place butter and sugars in the bowl of a mixer fitted with the paddle attachment and mix until light and fluffy. Add the eggs, one at a time and mix until smooth. Add the soaked oats and mix until incorporated. Add the dry ingredients and mix until just combined. Scrape the batter evenly into the prepared pan and bake in the oven until a toothpick inserted into the center comes out with a few moist crumbs, about 35 to 40 minutes. Place on a baking rack and let cool for 40 minutes; this cake is best served warm. Serve the cake topped with some of the warm berry compote and a large dollop of clotted cream.
Mixed Berry Compote:
2 teaspoons cornstarch
1 1/2 cups fresh orange juice plus 2 teaspoons
3 tablespoons honey
1 vanilla bean, split
1 cup fresh blueberries
1 cup fresh blackberries
2 cups fresh raspberries
For the compote: Dissolve the cornstarch in the 2 teaspoons orange juice. Set aside. Combine the 1 1/2 cups orange juice, the honey and vanilla bean in a medium saucepan and bring to a boil over high heat, let cook for 2 minutes or until the honey has completely dissolved. Add the blueberries and blackberries and cook for 2 minutes. Add the cornstarch and cook until the mixture thickens slightly, about 2 minutes. Remove from the heat and fold in the raspberries. Discard the vanilla bean. Serve warm.