In a medium bowl, stir together the Greek yogurt, honey, and vanilla extract (if using) until smooth and evenly combined. Taste and add more honey if you prefer sweeter yogurt.
If caramelizing the bananas, heat the butter in a small skillet over medium-high heat. Add banana slices in a single layer and cook for 60 seconds per side until golden brown. Set aside to cool slightly. Skip this step for raw bananas.
Grab 4 clear glasses or jars. Spoon 1/4 cup of the honey yogurt mixture into the bottom of each glass, spreading it evenly.
Layer 4-5 banana slices over the yogurt in each glass, pressing them gently against the sides for visibility.
Add 2 tablespoons of granola over the banana layer, then repeat the layering process — yogurt, banana, granola — until glasses are filled, ending with a yogurt layer on top.
Top each parfait with a final sprinkle of granola, a drizzle of honey, and a light dusting of cinnamon. Serve immediately for maximum crunch, or refrigerate covered for up to 2 hours before serving.