It helps to have your wet ingredients at room temperature.

1. Warm milk to 100-110 degrees.
2. Mix warm milk, brown sugar, yeast, pumpkin puree, oil, sourdough discard, and vanilla in a large mixing bowl and mix well. Next, add flour, salt, and spices and mix with a dough whisk or wooden spoon until a slightly sticky dough forms and all ingredients are thoroughly combined.
3. Cover and let rest for about 30 minutes in a warm spot. 
4. Perform one round of stretch and folds.
5. Cover bowl tightly and place in refrigerator overnight.
6. After chilling overnight the dough will be doubled in size. Dump onto floured surface and press or roll out to about a 1-inch thickness. Cut rounds with a 3-inch round biscuit cutter or drinking glass/jar. Reshape scraps by stacking them, re-rolling, and cutting. I like to get about 9-10 but if you like thinner English Muffins you can roll them a bit thinner and get a few more. This recipe is easily modified to your preferences.
7. When you have all muffins shaped, place them on a pan lined heavily with cornmeal or semolina flour - do not use parchment - Dust the tops with a bit of cornmeal or semolina as well. Cover the muffins and allow to rise for about 30 minutes or up to an hour until they are puffy and light. If your dough came straight from the refrigerator or your kitchen is chilly this can take about an hour. You want these nice and puffy before you fry them.
8. Preheat an electric skillet to 300 degrees or a heavy skillet over medium-low heat, and place risen muffins in, leaving a bit of space between each one. Cover and cook for 6-7 minutes. Flip and cook on second side for another 6-7 minutes, covered.
9. At this point, if your muffins are on the thicker side, reduce the heat to about 250 on an electric skillet or low on the stove, flip the muffins a few more times until the internal temp registers 195-200 degrees F. You can also pop them in a 350 degree oven for about 10 minutes to finish cooking. This extra cooking time will depend on the thickness. I like mine on the thicker side so I almost always give them an extra few minutes in the pan. 
10. Remove to cooling rack and allow to cool to room temperature.
11. For the best craggy nooks and crannies, use a fork and your fingers to pry the halves apart before toasting.

*Alternative shaping option:

Rather than rolling and cutting into rounds, you can divide the dough into 8-12 pieces, form each piece into a ball, and press the ball into a flat disk. This is for the people who hate dealing with scraps.