Potato-Scallion Ravioli

combine potatoes, grated cheese, and egg whip until smooth, thinning with milk as necessary season to taste with salt and white pepper place a teaspoon of potato mixture onto the center of each wrapper brush edges with water, fold in half, and press to seal repeat with remaining filling and wrappers place onto a sheet of waxed paper and freeze until firm simmer in boiling salted water for 5 minutes, drain well transfer to a heated serving platter cover with foil to keep warm heat butter in a saucepan, over a medium flame add thyme-mix well spoon over ravioli garnish with tomato concasse serve warm