In a large bowl, combine yeast and 1 cup warm water. Let stand for 5 minutes, then add warm milk, melted butter, sugar, and salt. Add flour and rosemary, and stir until batter is slightly elastic. Cover with a clean, moist kitchen towel, and let dough stand at room temperature for 45 minutes.
In a small bowl, combine baking soda and remaining ¼ cup warm water; stir mixture into batter. Re-cover, and let rise 20 to 30 minutes more.
On an oiled griddle over medium-low heat, ladle approximately ¼ cup batter into greased 2½ -inch round stainless-steel rings. Cook until tops of crumpets look dry, about 15 minutes.
Carefully remove crumpets from moulds. Flip crumpets, and cook until golden brown and cooked through, about 5 minutes more. Repeat with remaining batter; set crumpets aside.
Preheat oven to 350 º.
Slice crumpets in half horizontally, and place on a baking sheet.
Bake until lightly toasted, 5 to 10 minutes. Remove from oven, and let cool.
In a separate small bowl, beat cream cheese and goat cheese with a mixer at medium speed until smooth.
To assemble, spread approximately 1 tablespoon cheese mixture onto bottom half of a crumpet. Top with 2 spinach leaves, 2 radish slices, a slice of ham, and top half of crumpet. Repeat with remaining crumpets and sandwich fillings. Garnish with whole-grain mustard, if desired. Serve immediately.
Recipe by Victoria at https://victoriamag.com/rosemary-crumpet-sandwiches-recipe/