Preheat the oven to 200 C / 180 C fan / Gas 6. Grease a 12-hole mini-tartlet tin.
Brush 3 large sheets of filo pastry with melted butter and place them on top of each other like a sandwich. Cut the pastry lengthwise into 4 strips of equal width, then divide each strip into 3 rough squares to make 12 squares total. Place the squares into the holes of the prepared tin.
Bake until golden and crisp, about 8 to 10 minutes. Remove from the trays and put on cooling racks. Repeat this with the remaining 3 filo sheets to make 24 baskets.
For the prawn cocktail filling: Mix the prawns with the mayonnaise, tomato ketchup and Tabasco. Squeeze in the lime juice and add the dill. Season to taste. Divide among the filo baskets and finish each with a small sprig of dill.