How to Make It
Melt butter in a large saucepan over medium-high until sizzling, 1 to 2 minutes. Sprinkle with flour, whisking until smooth. Cook, whisking constantly, 2 minutes. (Flour will brown as it cooks, but if it starts to scorch, reduce heat as needed.) Add warm broth in a slow, steady stream, whisking constantly. Cook, whisking often, until gravy comes to a simmer and thickens, 6 to 9 minutes. Remove from heat, and let cool 30 minutes. Pour into a bowl or jar; cover and refrigerate up to 3 days.
To serve, reheat gravy over low. Stir in cream, sherry, thyme, pepper, and salt.