I've just proofed a sachet of dried yeast and it seems to be fine (it's still foaming up the glass as I type). Can I go ahead and use that very same batch of yeast to make bread (by including its liquid volume in the total ingredients) or it is now spent? It seems like a waste not to use it.
Yes, normally you proof yeast in part of the liquid from the recipe you are about to make. If it is active, you continue to use the proofed mixture directly in the recipe.