Preheat the oven to 350 degrees Fahrenheit.

In a large bowl, toss together peaches, berries, brown sugar, one tablespoon plus one or two teaspoons cornstarch (use two teaspoons for a thicker filling) and vanilla.

Spread the fruit out into a 10-to-12-inch baking dish.

To make the topping, combine the flour, oats, brown sugar, 1/2 teaspoon cinnamon, and a pinch of salt in a medium bowl. Add 8 tablespoons margarine, cutting the margarine into the dry ingredients with a fork. Crumble the mixture and sprinkle over the fruit. Cover with foil and bake 30 minutes.

Meanwhile, add remaining four tablespoons margarine to a small pot and set over medium heat. Allow the margarine to brown lightly until it smells toasted, about two to three minutes. Remove from the heat and whisk in the maple syrup, remaining 1/2 teaspoon cinnamon and a pinch of salt. Remove the crisp from the oven, remove the foil, and drizzle the syrup over the crisp. Bake uncovered for another 25 to 30 minutes.

Let cool slightly. Can be served as dessert alongside a scoop of ice cream.