Preheat grill to medium-high and coat with oil.
Season both sides of each salmon fillet with salt and pepper and place on the grill. Grill until the center is still slightly pink, 6 to 8 minutes total, rotating fish 90 degrees halfway during cooking on each side to obtain hash marks. Remove from the grill.
Meanwhile, make the pear butter sauce: In a medium saucepan, combine the diced pears, sugar, and hard cider. Cook over medium-high heat until the pears are translucent, about 5 minutes. Add the cream and cook until reduced by half, about 6 minutes. Add the butter several pieces at a time, whisking constantly to blend, and removing from the heat periodically to prevent the sauce from breaking. Add 1/4 teaspoon salt and 1/8 teaspoon white pepper and whisk to blend. Remove from the heat and cover to keep warm until ready to serve, stirring occasionally. (Do not allow sauce to boil or it will separate.)
Place the salmon on the plate with the roasted potatoes, drizzle the pear butter over the salmon and serve immediately.
Preheat oven to 400 degrees F.
Halve any larger potatoes so that they will all be about the same size. Put potatoes in a large bowl and season with olive oil, salt, and pepper, tossing to coat. Transfer potatoes and any oil from the bowl to a parchment paper-lined baking sheet and spread into a single layer. Roast for 20 minutes, stirring potatoes halfway through with a long-handled spoon. Remove potatoes from oven and sprinkle with freshly minced herbs and garlic. Return potato mixture to the oven and roast an additional 15 minutes or until tender.