Preheat the oven to 360°F.
Chop the walnuts.
Combine all the dry ingredients (flour, sugar, baking powder, cinnamon, salt and walnuts) in a bowl.
Combine the wet ingredients (egg, oil and vanilla extract) in another bowl.
Add the wet ingredients to the dry ones and stir only 3-4 times.
Grate the carrots and apple and add to the rest of the ingredients.
Line a muffin tray with paper or use silicone molds.
Place 1 large tablespoon of muffin mixture to each cup.
Add 1 teaspoon ricotta cheese.
Divide the remaining mixture into 6 equal portions and cover the cheese.
Bake for 25 minutes in the preheated oven.