Combine the dry ingredients. Put the flour, yeast, sugar, psyllium husks and salt in the bowl of a stand mixer fitted with the paddle attachment. Mix well on low speed.
Make the dough. Add the butter and 1/2 cup buttermilk to the dry ingredients and blend them together on medium-low speed. (The dough should be soft and cohesive. If the dough feels too dry, dribble in a bit more of the buttermilk until the dough is pliable.) Let the mixer run for 5 minutes. Scrape down the sides of the bowl and form the dough into a ball. It should be a bit sticky.
Rise the dough. Transfer the dough to a large bowl and cover with plastic wrap. Set the bowl in a warm place and let the dough rise for 90 minutes. (Unlike gluten dough, this dough will not double in volume. Instead, this rising time allows the dough to fully hydrate and rise a bit.)
Proof the dough. Line a baking sheet with parchment paper and set aside. Turn the dough out onto a clean surface and cut it into 6 equal pieces. Knead 1 piece of dough for a moment to release air pockets, then roll it into a ball. Repeat with the remaining pieces of dough, arranging balls on the prepared baking sheet, evenly spaced apart. Cover with a kitchen towel and let them sit in a warm place for 1 hour.
Prepare to bake. Preheat the oven to 350 degrees F. Dust the tops and bottoms of each ball of dough with cornmeal.
Griddle the English muffins. Set a large cast-iron skillet over medium heat. (An electric griddle works well too.) Lightly grease the pan with oil or butter. Put 3 balls of dough into the hot skillet and flatten them a bit with the palm of your hand. Cook until the bottoms of the English muffins are browned, about 5 minutes. Flip and cook them for another 5 minutes.
Bake the English muffins. Transfer the skillet to the oven and bake until the sides of the English muffins feel set, about 5 minutes. Move the English muffins to a cooling rack.
Repeat with the remaining 3 balls of dough.
Cool the English muffins completely before splitting them open and eating them.