Preheat oven to 350 degrees F. Grease 24-cup mini-muffin tin.
In a large saucepan, whisk together sugar,cinnamon, cornstarch, water and lemon juice. Bring to a boil over medium heat, stirring often. Cook until thickened, about 2-3 minutes. Remove from the heat and stir in vanilla and peaches. Cool.
Combine flour, oats and brown sugar in a large bowl. Cut the butter into the flour mixture with a pastry cutter until the mixture looks like coarse crumbs.
Place a heaping tablespoon of the crust mixture into a mini muffin cup. Press along the bottom and sides to make a “cup”. There will be crust mixture left over.
Place about 1 tablespoon of peach filling in the crust. Sprinkle about 1 teaspoon of the remaining crust mixture on the filling.
Bake in the preheated oven until golden brown, 15 to 20 minutes. Cool in the pan for 10 minutes. Use a knife to loosen from pan and they should pop right out.
Drizzle with sugar icing or caramel topping if desired, or small scoop of vanilla ice cream on a warm, sweet, amazing crisp.