For Brioche: Sprinkle yeast over milk in large mixing bowl; let stand 5 minutes. Combine flour, sugar and salt, beat in alternately with eggs and blend until dough is very smooth and elastic. (For best results, use standard mixer with a paddle attachment, mixing for approximately 10-15 minutes total.) Beat in butter, a tablespoon at a time, until well incorporated (dough will be very soft and sticky); continue to mix for 3 minutes more. Remove dough from bowl and shape into a ball.
Transfer to a large buttered bowl, cover with plastic wrap and let rise in a warm place until doubled in size, approximately 2 hours. Punch down, reshape into a ball, cover and refrigerate overnight.
After refrigeration, preheat oven to 375 degrees. Turn dough out onto lightly floured board; quickly form into loaf shape. Place dough in buttered 8x4-inch loaf pan; let stand at room temperature 20 to 30 minutes, or until dough just begins to soften (dough will rise slightly).
Transfer dough to oven, lower the temperature to 350 degrees and bake until golden brown and loaf sounds hollow when tapped, about 50 minutes. Let cool for several minutes, unmold while still warm and transfer to a wire rack to cool to room temperature.
Prepare the chocolate sauce:
Break up the chocolate and place the pieces along with 1/4 cup of the water in a saucepan. Place over low heat and slowly melt the chocolate, stirring occasionally.
When the chocolate is melted and smooth, stir in the butter piece by piece.
Stir in the rest of the water and bring the sauce to a boil, stirring constantly. Keep over very low heat while you finish the French toast. (The sauce may be made ahead. Reheat gently in a double boiler.).
For the French Toast:
Place a cake rack over your sink.
In a small bowl, stir the cinnamon and sugar together.
Place the brioche in one layer in a baking dish or other shallow dish and pour warm milk over them.
After about 1 minute turn them over and soak for another minute. Remove them to the cake rack to drain.
Preheat the oven to warm and place 6 plates or soup plates in the oven to warm.
Beat the eggs together in a shallow dish.
Place a frying pan over moderate heat and melt some butter in it. Quickly dip the brioche, first one side then the other.
Place in the frying pan and brown on both sides. Remove, place on a cutting board and sprinkle with the cinnamon sugar and Cocoa Powder. Repeat with remaining french toast/Brioche.
Cut the brioche into 6 pieces.
Place 5 pieces of brioche on each plate and drizzle with the chocolate sauce.
Cover with sliced large, ripe juicy strawberries and Pistachios (optional) and sprinkle lightly with confectioners sugar.