In a large bowl, mix together bread flour, yeast, 1 tsp salt, and 1 tablespoon of sugar.
In a separate bowl or cup, whisk together the water or coffee, whole milk, and 1 egg, and pour into the flour mixture.
Knead until a shaggy dough forms, about 2-3 minutes. Then, dump your dough onto a clean work surface and knead for 10-15 minutes until elastic and smooth.
Transfer dough to a clean bowl that’s lightly greased with oil. Cover with plastic wrap and let proof on the counter for 1 hour. Then, transfer to fridge overnight.
The next day, preheat oven to 450°F. Remove dough and knock the air out of it by gently pressing down. Place a pizza stone or baking sheet in your oven.
Form your dough into two equal baguette shapes, about 14 inches in length, on two pieces of parchment paper and cover with a damp towel, letting rest for 15-20 minutes in a warm place before baking.
When ready to bake, slide your bread onto the preheated pizza stone and throw a few ice cubes into the bottom of the oven for steam.
Cook for 12-15 minutes, until deeply golden brown. Let cool slightly and slice into crostini-shapes.
Transfer bread slices to a baking sheet and leave in a warm oven for 1-2 hours until stale. Alternatively, you can bake at 350°F for 10-15 minutes or leave bread uncovered overnight.
To make custard, whip 5 eggs and 1 egg yolk with 1/3 cup white sugar, 1/3 cup brown sugar, and 1 tsp salt in a large bowl until light and fluffy.
In a large microwave-safe pyrex or bowl, combine 1 cup heavy cream and 1 cup light cream and heat for 2 minutes, or until steamy. Add your espresso powder and stir. Cool to room temperature.
Grease a 9 x 9 square baking dish with butter. Pour your cream mixture into your whipped eggs and sugar and bring together into a custard.
Add your stale bread pieces and allow to soak for at least 30 minutes. Place your bread pieces into the buttered baking dish and pour any remaining custard on top.
Cover and rest for at least 1-2 hours in the fridge, or overnight.
When ready to bake, preheat oven to 375°F and cook for 35 minutes or until golden brown.
Whip 1/2 cup heavy cream with 2 tbsp white sugar (and add vanilla or any flavoring you like). Add mascarpone (optional) for a more tiramisu-like taste.
Serve warm bread pudding with a dollop of whipped cream.