Bake the garlic
Trim about 0.5 cm 1/4 inch off the top of the head of garlic (that will expose the garlic cloves). Season the garlic with salt and pepper and drizzle with olive oil. Wrap twice in aluminum foil. Place in a baking dish and bake for about 90 minutes at 190 °C / 370 °F. Remove from the oven and set aside.
Cook the onion
Set a pot with butter over medium-high heat. Dice the onion. Add the diced onion and thyme leaves to the pot. Cook for about 5 minutes, then add the flour and cook for another 5 minutes, stirring occasionally.
Cook the garlic soup
Press on the bottom of a clove to push the garlic out of its paper and into the pot. Add the dijon mustard, nutmeg and apple cider vinegar or lemon juice. Season with pepper, then add the white wine, stir well. Add vegetable (or chicken stock or water), milk and singe cream. Bring to a boil, then lower the heat and let it simmer for about 10 minutes.
Make the croutons. Cut bread slices up into small cubes. Add to a baking dish, drizzle with olive oil, sprinkle with parmesan cheese and season with pepper. Toss with your hands. Place in the oven and bake for about 12 minutes at 180 °C / 370 °F.
Blend the garlic soup using an immersion blender. Serve with croutons, fresh thyme and a drizzle of olive oil. Enjoy.