Preheat oven to 375 degrees F. Have ready a rimmed baking pan and 4 lightly greased ramekins large enough to hold ⅔ cup of raspberries and some crumb.
Melt the butter using gentle heat. You can do it over the stove or better yet, in a small microwaves-safe bowl using 50% power. Let it cool.
In a mixing bowl, combine berries, sugar and cornstarch and stir well to coat berries. Divide them between the ramekins.
In the bowl you used to mix the berries, mixt together brown sugar, flour, cardamom, salt and oats. Add the cooled melted butter and stir until mixture is crumbly. Sprinkle evenly over the berries.
Bake the crisps for 20-25 minutes, or until topping is browned. Let cool for about 5 minutes before serving.