Place the olive oil in a small sauce pan.

Cut the stem end off of the head of garlic and place the head cut side down in the sauce pan.

Cover and place in the oven for 35 minutes.

Remove and let cool. (The garlic may be roasted a few days ahead of time and refrigerated until needed.)

Place the sausage in a large skillet over medium high heat.

Cook for about 5 to 7 minutes, stirring frequently.

Add the onion and sage.

Cook for about 10 to 15 minutes. Stir frequently, and adjust the heat so the onions brown but don't burn.

Set aside.

Place the eggs, milk, mustard, and roasted garlic in a blender and puree until smooth.

Cut the bread into 1/2 inch cubes and place in a large mixing bowl.

Add the onion and sausage mixture.

Add the garlic, milk, and egg mixture to the bowl with the bread, onions, and sausage, and fold together.

Place the mixture in a 6 inch square Pyrex dish or divide it between 4 ramekins that have been lined with foil.

Bake in the oven at 325°F for 45 minutes.

Let cool slightly before serving.