Cut 1 centimeter off the top of the baguette. Scoop out the insides with a spoon leaving some of the bread intact.
Combine onions, panko bread crumbs, milk, egg, nutmeg, salt and pepper in a bowl and mix to combine. Then add the ground beef and mix until sticky and well combined.
Arrange tomato slices inside the baguette. Then put half the ground beef mixture on, making sure to smooth it out to form a nice flat surface. Next, arrange the quail eggs, followed by the rest of the ground beef mixture. Top it all off with the pickles, ketchup and cheese.
Wrap the baguette with foil and bake for 30 minutes at 200 degrees C.