Melt butter in a saucepan over medium heat.
Add flour, onion powder, white pepper, and salt to the melted butter and stir to make a smooth paste (roux). Continue cooking over medium heat for 1-2 minutes, just until the roux begins to brown.
Whisk the mixture continuously while slowly adding chicken broth to the pan until a smooth liquid forms.
Add the water and bouillon and bring the mixture to a simmer. Continue whisking and heating until the gravy thickens, 1-2 minutes.
Season to taste with additional salt and pepper, if desired.
Remove from heat and serve over hot mashed potatoes.
Store in a sealed container in the fridge, for up to 7 days.
