Grease 2 or 3 crumpet rings (about 9 cm/3.5" wide) with melted butter. Brush a non-stick skillet lightly with melted butter and place the rings in the skillet.
Turn the stove to medium-high (or medium for strong stoves) and heat the skillet and rings. Test with a drop of water—it should sizzle gently.
Pour about 1/4 cup (65ml) of batter into each ring, filling to about 1cm (2/5") deep.
Cook for 1 1/2 minutes. Bubbles should start to appear on the surface.
Reduce heat to medium and cook for another 1 minute. Some bubbles, especially around the edges, should begin to pop.
Lower heat to medium-low and cook for a further 2 1/2 to 4 minutes, until the surface is set and no more bubbles are forming. Use a skewer to pop any stubborn bubbles if needed.
Run a knife around the inside of each ring to loosen, then lift the rings off.
Flip each crumpet and cook the other side for 20–30 seconds, just until lightly golden.
Transfer crumpets to a wire rack, golden side down, and let cool completely.