Preheat the oven to 350°F.
In a large 10-12 inch skillet, sauté the bacon until 80-90% cooked - fat reserved.
Add the butter. After the butter has melted, add the leek and celery.
Cook, stirring occasionally, for about 5 minutes, until the leek mixture is soft and translucent. Add the sage and thyme in the last minute of cooking. Remove from the heat.
Place the corn bread and the croissant in a large mixing bowl and toss in the leek-herb and bacon mixture.
In a small bowl, combine the broth, cream and eggs and stir together. Incorporate this into the bread mixture and season with the salt and cayenne.
Return to the skillet to bake, uncovered, until golden brown on top. This should take 45 minutes to 1 hour.
Preheat oven to 425°F. Coat a 9- or 10-inch cast-iron skillet with the bacon grease and place it in the oven to heat while you mix the batter.
Combine the cornmeal, flour, sugar, baking powder, salt, ground fennel seed, and baking soda in a large bowl and stir to mix. Add the buttermilk, eggs, and butter and stir until just combined; do not over-mix. The batter should be lumpy.
Pour the batter into the hot skillet and sprinkle the top with a little salt and the whole fennel seeds.
Bake until the top is golden brown and a sharp knife or cake tester inserted in the center comes out clean, about 25 minutes.