In a bowl, place the whole milk, sugar and yeast and stir. Let it sit for 15 minutes until the yeast activates. Once activated, add in the buttermilk and mix until it is all fully integrated.
In a different bowl place the flour and salt. Add the yeast mixture and mix with a wooden spoon until a dough forms.
Place this dough on a clean and floured working surface and knead for 10 minutes until you get a really soft dough. Incorporate the butter and shortening and keep on kneading for another 10 min. until the dough becomes elastic and even softer (this whole process can also be done in a standing mixer with the dough hook attached).
Make a ball with the dough, coat it with some vegetable oil to then place it in a bowl and cover it with plastic wrap or a kitchen towel. Let it rise for 2 hours until it doubles its size.
Once that happened, place it on the clean a floured working surface and cut it into 10 same size pieces. Make a small ball with each piece and the roll each one out using a rolling pin or your hands, just to flatten them to be 1/2 inch (1cm). Place each shaped english muffin on a baking sheet previously greased and floured with some yellow cornmeal and cover them with a kitchen towel for them to rest for 1 hour, until they double their size.
Preheat the oven to 400° F (204° C) and, when there are 20 minutes left for the resting hour to be completed, heat to medium heat a big pan. Once the pan is hot, place 6 muffins and let them turn golden cooking them for 5 minutes each side.
Repeat the previous step until all the muffins turn golden brown, place them on the same baking sheets and bake them at 400° F (204° C) for 10 minutes until they are fully cooked.
Let them cool down before eating. When cutting them open is important to do it with a fork and not a knife, so that they stay fluffy.