1. In a mixing bowl, combine flour, salt, sugar, and baking powder.
2. In another bowl, mix warm water, warm milk, and yeast. Let it sit for 5 minutes until frothy.
3. Pour the wet ingredients into the dry ingredients. Whisk until smooth.
4. Cover the bowl with a cloth and let the batter rest for 30 minutes.
5. Heat a griddle or frying pan over medium heat and grease it lightly.
6. Place crumpet rings on the griddle and pour batter into each ring, filling halfway.
7. Cook until bubbles form on the surface and the edges look set, about 5 minutes. Remove the rings and flip the crumpets to cook the other side for 1-2 minutes.
8. Serve warm with butter and jam.