Pre-heat the oven to 400°F.
Bring a large pot of water to a boil. Blanch the broccoli rabe to remove the bitterness, about 2-3 minutes. Using a spider, drain the broccoli rabe and quickly cold shock it in a bowl of ice water.
Over medium-high heat, place a large skillet with two turns olive oil. Grate the garlic into the oil and add the red pepper flakes or Fresno pepper. Add the broccoli rabe and season with nutmeg, salt and pepper; cook for 2-3 minutes.
In another skillet over medium-high heat, heat remaining the tablespoon olive oil. Add in the sausage and cook until brown. Season with salt and pepper. Remove from the heat; drain the fat and allow to cool.
Cutting lengthwise, remove the top quarter of the loaf of bread and scoop out the insides of the bottom. Reserve the top piece.
In the bottom of the bread, layer ricotta, sausage and broccoli rabe, and top with provolone. Place the bread top back onto the bread, wrap the bread in foil and place it into the oven for 12-15 minutes.
Remove from the oven, allow to cool for a few minutes and slice.