Break the thirty grams of walnuts into coarse pieces or finely chop them with a sharp knife. If desired, roast the pieces for a few minutes in a dry frying pan over medium-high heat to deepen the flavor. Remove the pan from the heat and allow the nuts to cool completely on a cold plate.
Scoop the two hundred grams of full-fat Greek yogurt into a spacious breakfast bowl. Stir the yogurt firmly with a spoon first, so the texture becomes even and smooth before adding the dry ingredients.
Sprinkle the tablespoon of broken flaxseed over the loosened yogurt. Fold it in with gentle movements so it's distributed evenly throughout, allowing the seeds to be well incorporated into the dairy and absorb some of the moisture.
Finally, distribute the cooled walnut pieces over the top of the yogurt mixture. Serve immediately so the nuts retain their crispy texture and do not become soft from the yogurt.