Peel, core, and thinly slice pears. Layer pear slices, sprinkling raisins among the slices, in a buttered 9 x 13-inch pan.
Sprinkle with lemon juice and nutmeg; reserve. Mix flour, brown sugar, and salt.
Cut in butter until mixture resembles coarse cornmeal; work in cheese.
Sprinkle cheese mixture over pear mixture.
Bake at 325° F until the pears are just tender and the cheese mixture has browned lightly, about 35 minutes. Remove from oven; cool 15 minutes. Cut into 12 squares. Serve warm or at room temperature.
Top 1 square with a dollop of créme fraîche; dust lightly with nutmeg.
