Place the pineapple in medium pot; pour in 1-1/2 cups of the pineapple juice. Bring to a simmer. Place the remaining pineapple juice and the cornstarch in a small bowl and whisk to combine. Add to the pot and return to a simmer. Cook until a clear sauce forms around the pineapple, about 2 minutes. Spooning the mixture into an 8-inch x 8-inch baking dish. Preheat the oven to 350 degrees F. Combine the ingredients for the topping in a medium bowl; spread over the pineapple. Bake for 30 minutes, or until the top is golden and filling is bubbling.