Heat oven to 350°F (177°C).
Mix the chopped apples, granulated sugar, flour, cinnamon, and vanilla in a small bowl.
Transfer the apple mixture to a 10-ounce ramekin.
In a separate small bowl, stir together the flour, oats, brown sugar, and cinnamon.
Cut the softened butter into small pieces and work it into the dry ingredients with a fork or your fingers until the mixture clumps together.
Scatter the topping evenly over the apples.
Place the ramekin on a small rimmed baking sheet.
Bake for 30 to 35 minutes, until the apples are soft and the topping is golden brown.
