Combine olive oil, minced garlic, salt, and pepper in a large bowl.

Add the mushrooms to the bowl.

Marinate the mushrooms in the mixture for at least 24 hours.

Preheat the oven to 425F.

Remove the mushrooms from the marinade.

Roast the mushrooms for 45 minutes.

Remove the roasted mushrooms from the oven and let them cool.

Coarsely chop the cooled mushrooms.

Set the chopped mushrooms aside.

Reduce the oven temperature to 350F.

Heat the remaining marinade in a large skillet over medium heat.

Saute the diced onion in the heated marinade for 7 minutes, or until translucent.

Add the chopped mushrooms and herbs (sage and rosemary) to the skillet.

Cook for 5 minutes.

Remove the mushroom mixture from the heat and let it cool.

Cut a hole in the top of the artisan bread loaf, about 1/2 inch down from the top.

Hollow out the loaf, reserving the soft breadcrumbs in small pieces.

Transfer the mushroom mixture to a large bowl.

Add about 1/2 cup of the reserved breadcrumbs to the mushroom mixture.

Sprinkle in the shredded Swiss cheese, salt, and pepper.

Add the beaten eggs mixed with nonfat milk.

Stir until the mixture is moistened throughout.

Stuff the mushroom mixture back into the hollowed-out bread.

Wrap the stuffed loaf completely in foil to prevent drying out.

Bake the loaf until the mixture is cooked through, for about 45 minutes.

Remove the loaf from the oven and unwrap the foil.

Let the loaf cool slightly before slicing.

Slice the loaf and serve with a tart green salad.