Place ¾ cup raisins in a bowl with warm water. Allow the raisins to soak while you start preparing the dough.
In a large bowl, add the ½ cup (100 g) active sourdough starter, 1 cup (240 g) milk, 2 tablespoons (30 g) butter, 2 tablespoons (40 g) honey, 3 cups (360 g) flour, 1 teaspoon (5 g) fine sea salt and 2 teaspoons ground cinnamon. Mix well. Cover and let dough rest for 30 minutes.
Drain the water from the raisins. Remove the dough from the bowl after rest time onto a lightly floured surface. Knead the dough for 5 minutes by hand or with a mixer. Then, incorporate the raisins into the dough with your hands. I found this to be easiest with my hands mixing in a small handful at a time. If using a mixer, add raisins in slowly so they don't all fall to the bottom of the bowl.
Once raisins are kneaded in, place the dough back into the bowl, cover it, and let it rest and ferment at room temperature for 6 to 12 hours. If room temperature is over 70°F, let 8 hours be max time for the bulk rise/fermenting. After the bulk rise at room temperature, you can proceed with following steps to bake or you can place the bowl of dough into the refrigerator for up to 24 hours to bake at a later time. (I often make the dough midday, let it bulk rise during the afternoon/evening, then place in the fridge overnight to bake in the morning.)
Turn the dough onto a floured surface, flour the top of the dough, and press it out using your fingertips until it is about 1 inch in thickness.
Use a 2.5 to 3-inch biscuit cutter (I use 2¾-inch) to cut rounds from the dough. Gather the dough scraps, press them together, and cut more rounds. You should end up with 8 to 12 english muffins depending on thickness and size of your biscuit cutter. Sprinkle the tops with a bit of whole wheat flour or cornmeal (optional) and place them on a parchment lined baking sheet about 2 inches apart form one another. Cover with a light towel and allow them to rest for 15 minutes up to 1 hour at room temperature. This last rest will help with the rise of the english muffins.
Preheat oven to 300°F and preheat your cast iron skillet, pan or Blackstone over medium low heat. Place 4 english muffin rounds into the skillet spaced 2" apart and cook the first side for 4 minutes. Turn the muffins over and cook for an additional 4 minutes. *If you have a lid that will fit over your skillet, you can use it to cover the muffins while cooking- this will help the inside bake quicker, otherwise we will finish baking them in the oven.
The english muffins often need a little extra time in the oven after lightly browning them on both sides in the skillet. The center of an english muffin should register about 200°F on a digital food thermometer if you want to check that way. Otherwise, if the English muffins are still doughy in the center, place in the 300°F oven for 10-20 minutes until cooked through. You can slice one open to check or use a food thermometer to check!
Enjoy!!