All-Purpose Flour (Best Option)
1 tablespoon per 1 cup of sauceAll-purpose flour contains moderate protein levels, which help develop enough gluten to thicken Béarnaise sauce effectively while maintaining a smooth consistency. The gluten network traps water and fat, stabilizing the emulsion.
When using all-purpose flour, whisk it thoroughly into the melted butter or reduction before adding the egg yolks to avoid lumps. Cook gently to prevent over-thickening or curdling.
Compared to bread flour, all-purpose flour yields a slightly less chewy texture but is ideal for sauces where a delicate mouthfeel is preferred, making it the best practical substitute.