Ingredients:

  • 800g Sourdough or Challah bread, cut into 1-inch cubes
  • 60ml Unsalted butter, melted
  • 4 Large Yellow Onions, thinly sliced
  • 30ml Extra virgin olive oil
  • 5g Salt
  • 15ml Balsamic vinegar
  • 8 Large Eggs
  • 750ml Whole milk
  • 250ml Heavy cream
  • 10g Fresh thyme, minced
  • 5g Fresh sage, finely chopped
  • 300g Gruyère cheese, freshly grated
  • 5g Black pepper, freshly cracked

Instructions:

  1. Cut your 800g of sourdough into 1 inch cubes and spread them on a baking sheet. If the bread is fresh, pop it in a 300°F oven for 10 mins to dry it out.
  2. Heat 30ml olive oil and 30ml butter in a large skillet over medium low heat. Add the 4 sliced onions and 5g salt.
  3. Cook the onions for 25-30 minutes, stirring occasionally, until they are deep mahogany and jammy.
  4. Pour in 15ml balsamic vinegar and scrape up all the brown bits from the bottom of the pan. Remove from heat.
  5. In a massive bowl, beat the 8 eggs. Slowly whisk in 750ml milk, 250ml heavy cream, 10g thyme, 5g sage, and 5g black pepper.
  6. Butter your 9x13 dish. Place half the bread cubes in the bottom, then top with half the onions and 150g of grated Gruyère.
  7. Add the remaining bread and onions. Pour the custard mixture evenly over the top, pressing down on the bread until every piece is submerged.
  8. Cover and refrigerate for at least 2 hours, though overnight (12-18 hours) is much better for flavor development.
  9. Preheat oven to 375°F. Sprinkle the remaining 150g Gruyère over the top.
  10. Bake for 45-55 minutes until the center is set and the cheese is bubbling and bronzed.