Combine flour, baking powder, and salt. Stir or whisk to thoroughly combine.
Cut in butter (I usually just use my fingers), chilling afterwards if necessary.
Add yogurt, starting with four tablespoons and adding more if needed, mix in with fork until dough just comes together.
Turn out onto a lightly floured surface and knead 2-6 times until it forms a cohesive dough.
Pat out the dough into a seven inch circle or square. But into four roughly equal pieces.
Place on a prepared baking sheet (I baked mine in a cast iron skillet) and bake at 400 degrees until lightly brown on the bottom, about 12-15 minutes.
While the biscuits are baking make the gravy
Sauté the mushrooms in a dry cast iron skillet over medium heat until they begin to soften and release their juices, about five minutes. Add butter and stir to combine. Add flour, stirring until no dry bits of flour remain, lower heat slightly, add rosemary and garlic and cook for another minute or two, stirring occasionally. Add sherry, whisking until thoroughly incorporated, add water, bring to a low boil, stirring often until sauce is smooth and desired thickness. Add salt and pepper to taste.