For the muffins:
1 cup all-purpose flour
1/2 cup whole wheat flour
1 1/2 teaspoons baking powder
1/2 teaspoon baking soda
1 teaspoon cinnamon
1/4 teaspoon nutmeg
1/4 teaspoon cardamom
1/4 teaspoon salt
3/4 cup granulated sugar
1/4 cup grape seed oil, canola oil, or other neutral-flavored oil
1/4 cup applesauce
1 large egg
1 yolk from a large egg
1/2 teaspoon vanilla extract
3/4 cup shredded zucchini, drained and squeezed (see Recipe Note)
1/2 cup diced apple (diced small)
For the oat crumble:
2 tablespoons unsalted butter, softened
1/4 cup brown sugar
1/2 cup quick oats
1 1/2 teaspoons cinnamon
2 tablespoons all-purpose flour
For the crème fraîche:
3/4 cup crème fraîche
1 tablespoon honey, or to taste
Preheat oven to 350°F. Line a 12-cup cupcake or muffin tin with liners and set aside. Sift together the dry ingredients for the muffins and set aside.
In the stand of an electric mixer, combine the sugar, oil, and applesauce. Add in the egg, egg yolk, and vanilla. Mix until combined. With the mixer on low, add the dry ingredients in two batches, making sure to scrape down the sides and bottom of the bowl in between additions. Fold in the zucchini and diced apples. Divided the batter evenly between the muffin cups.
For the oat crumble, stir together the butter and brown sugar in a small mixing bowl. Add in the oats, cinnamon, and flour until evenly combined. The mixture should be crumbly and not too wet.
Sprinkle about 2 teaspoons of the oat mixture on top of each muffin (unbaked). Bake in the oven for about 22 minutes or until a toothpick comes out clean when inserted into the center of a muffin.
Before serving, mix together the crème fraîche and honey to taste.