Toss the cubed apples with lemon juice in a medium bowl. Set aside the bowl.
Mix sugar, cinnamon and nutmeg in a small bowl and set aside.
In a small bowl, mix cornstarch with water. Set aside the bowl.
Melt the butter in a large pan over medium heat. When the butter melts, add the apples and stir until the apples are getting soft. Then add the sugar mixture. When the sugar melts and the mixture boils, add the cornstarch. Remove from the heat when the sugar thickens.
Preheat the oven to 350°F(177C°). Grease regular size cupcake pan and set aside.
Mix flour, ground cinnamon, cornstarch and baking soda in a big bowl. Set aside.
Place the butter in a large bowl and beat on medium speed for 1 to 2 minutes until it is soft with a hand-held mixer or with paddle attachment if using a stand-mixer. Add in the brown and white sugar and cream on medium speed until light and fluffy. Add the egg, mix well. Then, add flour mixture and mix until it is totally incorporated. Finally, add in the rolled oats and mix well. During these steps, stop the machine and scrape down the sides and bottom of the bowl with rubber spatula as needed to be sure they are all mixed.
The dough will be very sticky. (If you like you can keep the dough in the fridge for almost 30 minutes but actually, you don’t need to as it is easy to give a cup shape even the dough is sticky) Use a spoon to fill the muffin tin. Divide the dough into equally 10 pieces(a little more than 2 ½ tablespoons-55grams). Press them onto bottom and up sides to give a cup shape with a spoon.
Bake for 14 minutes or until they are golden brown. When the cookie cups are out of the oven, they’ll be puffed. Gently press the center with a small glass to give their cup shape again. Place a parchment paper under the glass to avoid the risk of sticking. Remove the cookie cups from the edges with a toothpick after they cool in the pan for 15 minutes.
Fill the cups with caramelized apples. If you don’t eat it immediately, fill the cups when ready to eat as the apples soften the crust.
*I use 105g(1/2 cup) sugar when I top the caramelized apples with ice cream. I drizzle extra caramelized sugar that is left in the pan over ice cream. If you eat it plain, you can use 70g (1/3 cup) sugar.
The calorie information above is an estimate that is provided by an online nutrition calculator.