For the confit: In a high-sided skillet, heat the butter and oil over medium heat. Add the onions, apple slices, salt, and pepper. Cook until the onions begin to soften, about 5 minutes. Add the vinegar, maple syrup, and thyme. Reduce the heat to low and cook, stirring occasionally, until onions and apples are very soft, about 50 minutes.
Place an oven rack in the center of the oven. Preheat the oven to 350 degrees F. Arrange the bread slices on a baking sheet in a single layer. Drizzle with oil and bake until lightly golden, 12 to 14 minutes. Remove the baking sheet from the oven and place the gorgonzola squares on top of the warm toasts. Spoon the confit on top of the cheese. Sprinkle with chopped thyme and serve.
Cook's Note: Freeze the gorgonzola for 20 minutes for easier slicing.