In a large mixing bowl, combine 1 cup of oatmeal with 1 cup of kefir. Stir well to ensure the oats are fully soaked. Let the mixture sit for about 10-15 minutes to allow the oats to soften. Soaking the oats in kefir helps them absorb moisture, leading to a tender muffin texture.

In a separate bowl, whisk together 2 eggs and 2 tablespoons of honey or syrup until well combined. Add the grated carrots and apples to the egg mixture, and stir until everything is evenly distributed. The eggs and honey provide moisture and sweetness, while the carrots and apples add natural flavors and nutrients.

Add the egg, carrot, and apple mixture to the soaked oats. Stir until all the ingredients are fully incorporated. Combining the wet and dry ingredients ensures that the flavors meld together evenly.

If using walnuts, chop them roughly and fold them into the batter. This step is optional but adds a lovely crunch and extra flavor. Walnuts add texture and a nutty flavor that complements the sweetness of the muffins.

Preheat your oven to 180°C (350°F). Lightly grease a muffin tin or line it with paper liners. Greasing the muffin tin or using liners helps prevent the muffins from sticking, making them easier to remove after baking.

Spoon the batter into the prepared muffin tin, filling each cup about three-quarters full. Filling the muffin cups to this level ensures they bake evenly and rise nicely.

Place the muffin tin in the preheated oven and bake for 20-25 minutes, or until a toothpick inserted into the center of a muffin comes out clean. Baking at this temperature allows the muffins to cook through evenly, resulting in a golden brown exterior and a moist interior.

Once baked, remove the muffins from the oven and let them cool in the tin for a few minutes. Transfer the muffins to a wire rack to cool completely. Cooling on a wire rack prevents the muffins from becoming soggy and allows them to firm up.