1. Place a rack in the middle of the oven and preheat to 450 degrees F.
2. Grease a small baking sheet with the butter. Peel and core the pears and cut each into 8 wedges. Toss the pears and sugar together in a bowl and place on the buttered baking sheet, cut-sides down. Roast for 15 to 20 minutes, or until soft and browned on the undersides. Transfer pears to a piece of waxed paper and let cool completely. The pears can be made up to 4 hours ahead.
3. Meanwhile, make the vinaigrette: In a blender, whirl the ½ cup cranberries, vinegar, molasses, and mustard until smooth and uniformly pink. Season with salt and pepper to taste. With the machine running, add the 1/3 cup oil in a slow, steady stream, and blend until smooth. Season again with salt and pepper, if necessary. Set aside.
4. Toast the almonds on a baking sheet for 3 to 5 minutes, or until lightly browned. Transfer to a small bowl to cool, then stir in the second ½ cup cranberries.
5. Make the blue cheese toasts: Reduce the oven temperature to 400 degrees F. Cut each slice of bread in half, so you have 16 halves. Brush both sides of each piece with some of the oil, and toast on a baking sheet for 3 to 4 minutes per side, until lightly browned. Remove from the oven, and divide the blue cheese between the toasts, crumbling the cheese up a little as you go. (The toasts can be made ahead up to this point and refrigerated, up to 4 hours.) Return the toasts to the oven and bake for 4 to 5 minutes, until the blue cheese has melted.
6. Place the spinach in a large bowl, add half the almond/cranberry mixture, add the vinaigrette to taste, and mix well. Arrange the dressed greens on a platter or on individual salad plates, and garnish with additional nuts and berries, roasted pears, and blue cheese toasts. Serve immediately.
Peel and core a tart apple instead of the pear.
Substitute goat cheese or a hard grating cheese, like Parmesan, for the blue cheese.
Substitute dried cherries for the cranberries.
Substitute coarsely chopped walnuts, pecans, pistachios, or your favorite nuts for the almonds.