Heat oil in a heavy bottomed skillet on medium-high heat. Saute the leeks with a pinch of salt and pepper, red pepper flakes, and 1/8 teaspoon cayenne. When the leeks are translucent raise the heat to high and add the sausage and cook for 8 minutes or until browned. Remove from heat and allow the mixture to cool.
In a separate bowl whisk the eggs together with the cream, milk, the remaining cayenne, a pinch of black pepper and salt.
Cut the baguette into cubes and put in the bottom of a 9 by 9-inch glass casserole dish. Sprinkle the bread with the Cheddar cheese. Pour the sausage and leek mixture and egg mixture on top. Top with pepper jack cheese. Cover tightly and refrigerate overnight.
Preheat oven to 375 degrees F.
The next morning remove from refrigerator. Put in the middle of the oven and bake for 45 minutes or until a knife is removed cleanly from the middle. Remove from oven and allow the casserole to stand for 10 minutes before cutting and serving.