1. In a large pot, cover the quartered potatoes and garlic cloves with cold water and bring to a boil. Simmer over moderate heat until the potatoes are tender when pierced with a fork, about 20 minutes.
2. Meanwhile, in a medium skillet, heat the canola oil until shimmering. Add the shallots in a single layer and cook over moderate heat, stirring frequently, until they are golden, about 15 minutes. Using a slotted spoon, transfer the shallots to paper towels to drain.
3. Drain the potatoes and garlic in a colander, shaking out the excess water. Add the half-and-half and butter to the pot and heat until melted. Remove from the heat. Press the potatoes and garlic through a ricer into the pot and season with salt. Stir and cook over moderate heat until very hot. Transfer the mashed potatoes to a bowl. Just before serving, sprinkle the shallots with salt and garnish the potatoes with the shallots.