In a large, heavy skillet, melt 2 tablespoons of the unsalted butter in 1 tablespoon of the olive oil. Add the chopped garlic and the remaining 1/4 teaspoon of cayenne pepper and cook the garlic over moderate heat, stirring, for 2 minutes. Add the baby spinach to the skillet and cook, turning, until the spinach is wilted, about 5 minutes. Season the spinach with salt and pepper. Transfer the spinach to a serving platter and keep warm.