Preheat the oven to 375°F. Get out four 2/3-cup baking dishes or ramekins., To make the filling: Blend the sugar and Instant ClearJel or cornstarch. Add the fruit and lemon juice and stir until combined., Divide among the baking dishes; there'll be about 1/2 cup filling per dish. Set aside., To make the topping: Whisk together the dry ingredients. Work in the butter just until the mixture is unevenly crumbly; it's OK for some larger chunks of butter to remain unincorporated., Add the milk and stir until everything is moistened and cohesive., Use a teaspoon cookie scoop or a spoon to drop balls of dough, about the diameter of a nickel, close together on top of the filling. Sprinkle with coarse sugar, if desired., Bake for 25 to 30 minutes, until the topping is lightly browned and the filling is bubbly. Remove from the oven, and cool at least 15 minutes before serving. Top with ice cream or whipped cream, if desired.