How to Make It
In a small skillet, toast the slivered almonds over moderately high heat, tossing occasionally, until they are golden, about 2 minutes; let cool.
Season the pork medallions with salt and pepper, then coat in the flour. In a large skillet, melt 2 tablespoons of the butter in the olive oil. Add the medallions and cook over moderately high heat until lightly browned on both sides and just cooked through, about 4 minutes. Transfer to a plate.
Add the onion to the skillet and cook over moderate heat until softened and just beginning to brown, about 4 minutes. Add the garlic and cook until fragrant, about 1 minute. Add the Riesling, stock, raisins, vinegar and thyme and bring to a boil. Cook over high heat, scraping up any browned bits from the bottom of the pan, until the liquid has reduced slightly, about 2 minutes.
Return the meat to the skillet and simmer until hot, about 1 minute. Transfer to a platter. Add the remaining 1 1/2 tablespoons of butter to the sauce and cook over moderate heat, swirling, just until the butter is melted. Pour the sauce over the pork, garnish with the toasted almonds and serve.