Preheat broiler. Melt 2 tablespoons of butter over low heat. Split the biscuits and line the bottom of the baking dish with them. Brush the split halves well with melted butter and toast under the broiler until golden and crisp.
In the skillet or sauté pan, melt the additional 2 tablespoons of butter and sauté the mushrooms well over medium heat. Stir in the scallions and bell pepper and cook until just wilted. Remove from heat and pour the vegetables into a mixing bowl with the corn, white pepper, cayenne, nutmeg, and salt. Preheat oven to 325°F (163°C).
Toss the shrimp with the sherry. Beat the eggs with the milk and pour over the vegetables. Arrange the shrimp over the biscuits. Stir any liquid into the vegetable mixture and pour over the shrimp and biscuits. Bake in middle level of oven for 50 minutes, or until custard is set. Do not brown or let puff.