Brush a large baking sheet with butter or oil. Put wheat flour with wholemeal flour and salt in a large bowl and make a well in the middle. Dissolve the yeast with the warm water and add to the flour. Use a wooden spoon to work the dough into a slightly sticky ball.
Knead the dough on a floured work surface for ten minutes to form a smooth and elastic dough. Work in the rest of the flour as needed. Put the dough in a large bowl and let rise in a warm place for an hour, covered.
After rising, knead the dough for a minute and roll it up tightly into a long stick. Let the ends come to a point so that a baguette shape is created. Place the dough on the prepared baking tray and let it rise for another 40 minutes in a warm place.
Preheat the oven to 210 degrees. Pour half a liter of hot water into a flat baking pan or casserole dish and place on the bottom of the oven. This gives the bread a crispy crust.
Brush the egg white on the bread. Cut the surface at an angle of about 5 cm with a sharp knife. Then bake in the preheated oven for 15 minutes. Then reduce the temperature to 180 degrees and quickly coat the baguette with the glaze again and bake for another 15 minutes.
Turn out and allow to cool on a wire rack. The baguette bread only tastes fresh on the same day.