Stir the fresh yeast into the lukewarm water until dissolved.
Add the Type 550 wheat flour, Type 1050 wheat flour, whole wheat flour, and salt.
Mix, then knead until the dough is smooth.
Stretch and fold the dough several times.
Cover with a kitchen towel and let rest for about 60 minutes, or until almost doubled in size.
Fold the dough again briefly.
Shape it into a long loaf.
Place the loaf on a well-floured baking sheet lined with parchment paper.
Let rise again for about 30 to 45 minutes.
Preheat the oven to 210°C / 410°F with top and bottom heat.
Score the bread lengthwise.
Place the bread in the oven and add a small oven-safe bowl of water to create steam.
Bake for 10 minutes at 210°C / 410°F.
Reduce the heat to 200°C / 390°F and bake for another 30 to 40 minutes.
Remove the bread from the oven and cool on a wire rack before slicing.