Starter:   Combine water, yeast and flour in mixing bowl; mix well to form a soft dough.  Cover and let rest at room temperature for around 14 hours.

Dough:  Combine starter, yeast, water, flour and salt in mixing bowl of a stand mixer.  Mix with beater until all ingredients have come together.  Switch to dough hook and knead for 5 minutes on speed 2 of stand mixer.

Place dough in lightly greased 8-cup measuring cup or medium-size bowl.  Cover with plastic wrap and let dough rise for 3 hours, gently deflating it and turning it over after 1 hour, and then again after 2 hours.

Turn the dough out onto a floured surface and divide into whatever portions you want.  This recipe makes 42-ounces of dough.  I made two baguettes and three stuffed baguettes, so I divided the dough into two 12-ounce portions for the baguettes and three 6-ounce portions for the stuffed baguettes.

For the Baguettes:   Working with one piece at at time, flatten the baguette dough into a rough rectangle.  Fold the dough in half lengthwise, and seal the edges with the heel of your hand. Flatten it slightly, and fold and seal again. With the seam-side down, cup your fingers and gently roll the dough into a 15" log. Place the logs seam-side down onto a lightly greased or parchment-lined sheet pan or perforated French bread pans.  Cover lightly with greased plastic wrap and allow to rise until they have become very puffy, about 1½ hours.

Towards the end of the rising time, preheat oven to 425° F.  Using a very sharp knife or single edge razor blade held at about a 45° angle, make three 8" vertical slashes in each baguette. Spritz the baguettes heavily with warm water; this will help them develop a crackly-crisp crust. Bake the baguettes until they're a very deep golden brown, 25 to 30 minutes. Remove them from the oven and cool on a rack. Or, for the very crispiest baguettes, turn off the oven, crack it open about 2", and allow the baguettes to cool in the oven.  Yield:  2 Baguettes.

For the Stuffed Baguettes:  Shape each of the 6-ounce pieces of dough into a rectangle.  Layer with Brie and ham; spread mustard on the ham.  Roll up like a jelly roll, sealing the long seam and pinching the ends closed.  Place on a lightly greased or parchment-lined baking sheet or a perforated French bread pan.

Slash each stuffed baguette several times with a very sharp knife or single edge razor blade held at about a 45° angle.  Bake at 425° F for 20 minutes, or until golden brown.  Cool on wire cooling rack.  Yield:  3 Stuffed Baguettes.