Scoop the full-fat Greek yogurt into a deep bowl. Roughly chop the walnuts so you can still taste the pieces.
Rinse the blueberries and let them drain briefly. Sprinkle the walnuts, berries and broken flax seeds over the yogurt.
Dust everything with a pinch of cinnamon for a warm, sweet note without sugar. Stir gently if you like to blend the flavors, or let the toppings sit beautifully on top.
Serve immediately while the walnuts are still crispy and the yogurt is chilled.