Preheat the oven to 200°C. Lightly coat eight 6-ounce ramekins with nonstick cooking spray and place on a rimmed baking sheet.
Toss the peaches with the cornstarch and 2 tablespoons sugar in a large bowl. Let stand until juicy, about 10 minutes. Divide the peaches and juices among the ramekins.
While the peaches sit, combine the flour, remaining 1/2 cup sugar, flax seed and salt. Cut in the butter, using a fork or pastry cutter, until the mixture forms medium-size crumbs. Stir in the buttermilk until well moistened and large clumps hold together.
Sprinkle the topping evenly over the peaches. Bake until the fruit is bubbling and the topping is golden brown and crisp, 40 to 45 minutes. Serve warm or at room temperature with vanilla yogurt or frozen yoghurt if desired.