Cut enough 1/2" thick slices of bread to cover the bottom of a 9X13 baking dish in one layer.
Arrange sliced bread on a baking sheet and bake 350 degrees for about 10 minutes, turning half way. (light color on the bread).
Butter the bottom of the baking dish and arrange toasted bread on bottom in single layer.
Fry bacon over medium heat till nice and crisp, remove and drain. Pour off all but 1 Tablespoon of bacon fat and return to heat.
Add THOROUGHLT WASHED chopped leeks and sautee till wilted, about 4-5 minutes. Scatter leeks over bread.
Chop bacon and break brie up into pieces. (hint, stick it in the freezer for a bit and it makes it easier to cut up) Evenly distribute brie and bacon over leeks and bread.
In a bowl, whisk eggs till blended, add half and half, and cayenne and continue to mix till just blended. Pour egg mixture into baking dish with all other ingredients. Cover with plastic or aluminum wrap, and refrigerate overnight.
Before baking: remove dish from oven 30 minutes to come to room temperature Preheat oven to 350 degrees. Bake on center rack until the top is golden and bubbly (about 50 minutes to an hour).
Remove from oven, allow to stand at least 5 minutes. Sprinkle with chopped parsley prior to serving. (Serve hot to warm).