To roast the garlic, preheat the oven to 350 degrees F. Slice off the top portion of the garlic head to reveal the cloves. Lightly rub back and forth to remove the paper and peel any excess paper off. Pour a bit of the oil over each bulb. Wrap the bulbs tightly in foil and place in the oven. Roast for 45 to 60 minutes, until the cloves are caramel and golden in color. You can do this process ahead of time!
Heat the oven to 400 degrees F. Line a baking sheet with foil and place the bread on the sheet.
Take the bread and make 1-inch slices ¾ of the way down into the bread, leave the whole loaf intact.
Place the butter in a bowl. Squeeze in the roasted garlic cloves. Add about 2 tablespoons of the pesto and stir and mash the mixture together. Take the butter and spread it inside every slice and crevice of the bread, reserving just a bit. You can use a little more of the pesto and spoon and spread it in the slices and crevices. Take the fontina cheese and stuff it inside the slices and crevices.
Brush the top of the bread with the remaining garlic pesto butter. Bake for 20 to 25 minutes, until golden and bubbly. Remove and sprinkle it with the parmesan. Serve while it’s hot!