What does it mean to "proof" yeast? Thank you!

If I have active dry yeast in a recipe, I'll usually take some of the liquid used in the recipe (in this case: cream)...usually just a couple tablespoons...and warm it just slightly in the microwave. Then I stir in the yeast and let it sit for a few minutes. After its dissolved and bubbly I'll add it in with the rest of the liquid.

Basically it means making sure your yeast is active before baking with it. This is usually done by mixing your yeast into warm (not hot, you don't want to kill the yeast!) water or milk with some sugar. In about 5-10min the yeast should "wake up" and your liquid will be foamy and frothy. If your yeast doesn't get foamy, it wasn't active to begin with and the bread would not have risen. Instant yeasts can be added dry, and the kneading/mixing process will distribute the yeast and give it enough liquid to wake up (though I've used regular active dry yeast straight into my dough and it still worked fine). But a lot of people "wake up" (aka proof) their yeast before they begin the bake regardless of the type of yeast. I don't see where this recipe says to proof the yeast, but if you want to proof it before baking subtract out the amount of liquid you used to proof the yeast from the total liquid you add to your dry ingredients. I wouldn't proof in a large volume of liquid because this recipe doesn't seem to use liquid beyond the water and cream for the roux-like paste.