Preheat oven to 450F.

To Make the Caramelized Onions: Add the butter to a large skillet over medium high heat. Once melted, add the thinly sliced onions to sauté 10-15 minutes. Add ¼ cup water, stir until evaporated, then repeat 2-3 times until onions are deeply caramelized. Deglaze the skillet with the white wine. Stir until the white wine has evaporated. Remove from heat.

To Make the Crostini: Add the baguette slices to a small baking pan. Drizzle generously with the olive oil, then bake 8-10 minutes, until golden and crunchy. Pulse in a food processor so you have a variety of tiny and larger pieces. Set aside.

To Make the Mac N Cheese: In a large skillet, preferably oven safe, add the butter. Once melted, add the garlic to sauté 1 minute. Add the flour and whisk until well incorporated in to the melted butter. Cook another minute.

Gradually whisk in the milk 1 cup at a time, making sure the sauce thickens before adding the next cup. Gradually whisk in the bone broth.

Gradually whisk in the heavy cream, then whisk in the spices and dijon.

Reduce heat to medium. Set aside half of the grated gruyere cheese and ½ cup grated mozzarella.

Whisk in 1 cup of grated cheese at a time. If the cheese mixture begins to boil, reduce the heat immediately. Lastly, whisk in the egg yolk and fresh thyme.

Stir in the cooked pasta. (If needed, transfer to a larger 9×13” baking dish.)

Top with the remaining grated gruyere cheese and caramelized onions first, then the crostini bits.

Reduce oven heat to 400F to bake for 15-20 minutes, until cheese is melted on top. If at any point you find the crostini to begin burning, cover with foil. Let cool at least 10 minutes before enjoying warm!