- Preheat the oven to 350°F.
- Toss together the oats, walnuts, sunflower seeds, olive oil, salt, and cinnamon and spread in a thin layer on a baking sheet/tray. Toast until fragrant and slightly golden; 5 minutes. Cool.
- While the muesli bakes, make the walnut crumble. Toss together walnuts, sugar and a splash of water in a small pan over medium heat until the sugar caramelizes and glazes the walnuts lightly. Set aside to cool and roughly chop.
- Fill four bowls with 1/2 cup muesli each. Garnish with raisins, grated apple, and top with yogurt or kefir. Sprinkle each bowl with walnut crumble. Stir together and eat, with a touch of honey if desired.
*The remaining muesli and crumble can be stored in an airtight container.