Preheat oven to 425℉ and line a large baking tray with parchment.
In a large bowl whisk together flour, cornmeal, baking powder, baking soda and salt.
Add cubed butter and using a pastry cutter, cut butter into dry ingredients until pea-sized and evenly distributed.
Whisk together buttermilk and one large egg. Add to dry ingredients and stir until just starting to come together. Add grated cheese and diced jalapeno and continue to mix until incorporated being careful not to overmix. It will be a bit of a scraggly mess.
Flour your work surface and dump out the dough. Knead dough a few times to bring everything together. Flatten dough into a 3/4"-1" disk. Using a 3" round cutter, cut out biscuits.
Reform remaining dough and cut out biscuits. Place biscuits on a parchment lined baking tray.
Whisk together one large egg and one tbsp of milk or cream. Brush each biscuit top and sides generoulsly. Bake in preheated oven for about 18 minutes until golden and puffed.
Remove from oven and allow to rest on the tray for 3-5 minutes before moving to a cooling rack. Serve slightly warm.
-these particular biscuits spread out some and are wonderful sliced as a sandwich.
-I used a 3" cutter, however for slightly smaller biscuits that would be good for soups or stews a 2 1/2" cutter is probably preferred.