Bring broth to a simmer in a saucepan, reduce heat to low to keep mixture warm.
Heat butter in a large, deep skillet over moderate heat. Add onion, stirring until it begins to soften, about 2 minutes, taking care not to brown it.
Add rice and stir until grains are coated and begin to look translucent, about 2 minutes.
Add wine and stir until it is completely absorbed. Pour in about 2/3 of the simmering broth, stir well, and cover. Cook for 18 to 20 minutes, until rice is tender but still firm and the risotto is creamy, lifting the lid occasionally to stir and add broth if the mixture starts to look dry.
Remove lid and mix in sage, to taste, adding broth as needed. Cook uncovered for a few more minutes until rice is just tender. Stir in Gorgonzola and pear, mixing gently until the cheese melts and the pear is heated through. Season with salt and pepper to taste.
Serve and garnish with pear slices, fresh sage, and crumbled Gorgonzola.