Preheat a grill or grill pan. Alternatively, preheat the oven to 350 degrees F.
Slice the bread into 1/4-inch thick slices. Brush with olive oil, season with salt and pepper, and lightly grill on 1 side. Cool and store in a sealed container until ready to use.
Combine the harissa, sour cream, half of the lemon zest, and half of the lemon juice in a small bowl.
If more lemon is necessary, add the rest of the zest and or juice. Put into a squeeze bottle for easy assembly.
Preheat the oven to 350 degrees F. Coat lamb racks generously with the spice mix, salt, and pepper. Be cautious with the pepper since there is pepper in the spice mix. There should be an even coat of spices around the lamb. Heat a couple tablespoons olive oil in a very large skillet over high heat. When oil is hot, add lamb racks and sear over high heat to form a crust on both sides. Remove from the pan, transfer to a baking dish and finish in the oven for 8 minutes or until medium rare. Remove from the oven and allow to rest at room temperature for at least 5 minutes before slicing.
Assembly: Slice the lamb into 1/4-inch thick slices as close to the bone as possible. Place a piece of lamb on top of a baguette slice. Add a drop of the harissa (remember it is spicy), and then finish with a thin julienne of dried apricot and a sprig of chervil. For additional seasoning, add a sprinkle of salt and a drop of extra-virgin olive oil.
In a shallow saute pan, toast all of the spices over a medium heat. Allow to cool and then grind in a coffee grinder to a fine powder.