All-Purpose Flour (Best Option)
1:1 by volume (e.g., 1 tablespoon all-purpose flour per 1 tablespoon bread flour)All-purpose flour contains a moderate protein content (around 10-12%), which is slightly less than bread flour but sufficient to create a stable, thick gravy in Shepherd's Pie. The gluten network formed is enough to bind the filling without making it tough.
When using all-purpose flour, whisk it thoroughly into the fat or drippings before adding liquids to avoid lumps. Cook the roux slightly longer to develop flavor and ensure proper thickening.
The final filling will be slightly less chewy but still hearty and cohesive, preserving the traditional mouthfeel of Shepherd's Pie.