Heat the olive oil in a large skillet. Add the almonds and onion and cook over moderate heat until the almonds are golden, about 4 minutes. Add the grapes and garlic and cook for 2 minutes. Stir in the spinach in handfuls, adding more as the leaves wilt. When all of the spinach has been added, stir in the wine and butter. Season with salt and white pepper and serve at once.