In a skillet over medium heat, add a few tablespoons of olive oil. Sauté the Canadian bacon for a few minutes, or until it starts to develop browning. Once cooked, remove and set aside.

In the same skillet, add more olive oil if needed and sauté the spinach until wilted down, only a minute or two.

Grease a 13" x 9" casserole dish, and add the spinach and ham to the bottom of the dish. Evenly layer the torn croissants on top.

In a large mixing bowl, beat eggs and add half and half, shredded cheeses, dijon mustard, and salt and pepper. Stir to combine.

Pour the egg mixture over the croissants and toss to evenly distribute the ham and spinach throughout the casserole.

Cover the casserole and refrigerate for a few hours or up to overnight.

When ready to bake, heat oven to 375 degrees F. Bake covered for 40 minutes, and uncovered an additional 10 to 15 minutes, or until the center of the casserole reaches 165 degrees F.

Remove from oven and let cool a few minutes before serving.

Garnish with freshly chopped chives if desired.