Lightly steam Broccoli and dip in ice water to stop cooking and retain verdant greenness. Drain well. Cut the florets and edible stem into bite-size pieces. Set aside.
In a heavy soup pot, melt the butter and sauté the Onions, Leek, Celery, Carrots and Garlic over a medium heat until soft and translucent, about 8 minutes. Sprinkle the flour over the vegetables and stir to make a roux, cooking for 2 to 3 minutes. Gradually add milk and broth, constantly stirring until smooth. Add the Thyme and Marjoram, and salt, pepper and freshly grated nutmeg to taste. Stir over low heat until thickened. Add the Broccoli. (It freezes well in airtight plastic bags for use within three months.) Serve piping hot with a optional sprinkling of grated cheddar cheese.