1. Preheat oven to 250 degrees. Bring water and 3/4 cup sugar to a simmer in a small saucepan over medium-high heat, stirring until sugar dissolves. Cook, swirling pan occasionally if sugar darkens unevenly, until mixture turns dark amber. Pour caramel into a 6 1/2-inch charlotte mold that's 3 1/2 inches deep, swirling mold to coat bottom and sides. (Caramel may crack as it cools.)

2. Place star anise in a small bowl. Combine salt and remaining 1/4 cup sugar in another small bowl. Place lemon juice in a third small bowl.

3. Peel 3 pears. Using a mandoline or a handheld slicer, slice each pear lengthwise 1/8 inch thick, stopping at the core and turning over to slice the opposite half.

4. Arrange 1 layer of pear slices in a tight, overlapping circle in mold, working counterclockwise to cover the bottom. Brush lightly with lemon juice, and sprinkle with 1 teaspoon sugar mixture. Arrange next layer of pear slices in a tight, overlapping circle, working clockwise to cover previous layer. Sprinkle with 1 teaspoon sugar mixture and a pinch of star anise. Repeat slicing and layering with remaining pears. Continue to switch directions, and alternate lemon juice and star anise. Leave 1/2 inch of space at the top of mold.

5. Cover mold with foil. Place in a large roasting pan, and transfer to oven. Carefully pour boiling water into pan to come halfway up sides of mold. Bake until a tester inserted into center meets no resistance, 1 1/4 to 1 1/2 hours. Transfer to a wire rack, uncover, and let cool for 10 minutes.

6. Place a pie dish or a rimmed plate over mold, and quickly invert. Remove mold. Using a spatula, transfer terrine to a platter, reserving sauce in dish.

7. Pour sauce into a small saucepan, and boil until slightly thickened, about 5 minutes. Let cool. Slice terrine, and serve warm with sauce and, if desired, blue cheese and walnuts.