Fry bacon in a large skillet until crisp. Transfer to paper towels and pour rendered fat into a small bowl, and set skillet aside.
Melt vegetable shortening and 2 tablespoons of the bacon fat together in skillet. Meanwhile, spray a 12-muffin tin or a 24- mini muffin tin with Pam.
Crumble bacon and set aside. Lightly beat eggs in a large bowl. Add bacon, onions, jalapenos, jalapeno pickling juice, sugar, baking soda, salt, cumin, and pepper and beat well. Add cornmeal and buttermilk and stir. Pour the hot fat from the skillet into the batter and stir until just combined.
Divide batter between the muffin cups. Bake muffins at 425 degrees until lightly golden and toothppick inserted in center comes out clean, about 15 minutes for large tins. Makes 1 dozen regular size muffins.