For the devil’s food chocolate cake:

1. Preheat oven to 350ºF /180ºC.
2. Butter a 9-inch and 6-inch (or two 8-inch) cake pans with removable bottoms. Dust with breadcrumbs.
3. Sift together flour, cocoa, baking powder and soda, salt.
4. In a large bowl beat butter until creamy, about 1 minute. Add sugars gradually and beat for 2 minutes after adding the last part.
5. Add eggs, one at a time, beating well after each addition.
6. Add vanilla and unsweetened chocolate. The mixture will look curdled, that’s fine.
7. Add the dry ingredients in 3 parts, alternating with the yogurt in 2 parts. Mix just until well combined.
8. Slowly add boiling water and mix just until combined.
9. Add the milk chocolate with a spatula, and divide between pans, using a bit more in the large one.
10. Bake for about 40 to 45 minutes, until a tester inserted in the middle of both cakes, comes out clean.
11. Let cool completely on a wire rack before filling and frosting. It can be made the day before and kept wrapped in plastic.

For the meringue:

1. Put a pan with water over medium heat.
2. On top of it, place the glass or metal bowl from the mixer with the whites and sugar. The water should not touch the bottom of the pan.
3. Mix constantly with a hand whisk. The water will start to boil. Don't let water get into the bowl.
4. The mixture will be thick at first but will liquefy as it warms. This is your cue to remove it. It will also be warm to the touch (use your pinky finger to test).
5. Transfer to the mixer (or mix with a hand-held electric beater) and whip until stiff and glossy, about 5 minutes. You should have rather stiff peaks.

To assemble the cake:

1. Cut both cakes in half. If you want to, dab the cake plate with a bit of dulce de leche in the middle and place one of the large layers on top; that way the cake won’t move.
2. Fill with a thick layer of dulce de leche, about ¾ of the amount, spreading evenly but not reaching the edges completely. Top with the other large layer, pressing gently. The dulce de leche will fatten towards the edges.
3. Add some meringue on top of the cake making a circle as big as the layers that you haven’t used yet. Place one of those layers on top, and fill with meringue, not reaching the edges completely.
4. Mix the rest of the dulce de leche with the meringue you have left, swirling just a few times to have a marble effect. (As you can see I didn’t quite get that effect, but not for lack of trying…).
5. Add a thin layer of meringue to all of the cake and then add a thicker one. However, you can. The meringue is soft for having a perfect frosting.
6. Sprinkle with the chocolate crumbs.