Gently warm your pre-cooked shredded birria meat and the birria consommé in separate small saucepans over low heat. You want them hot, but not boiling, so they're ready for assembly and dipping.

If your cheese isn't already shredded, get that done now. Shred the Oaxaca or Monterey Jack cheese. If you're using them, finely chop your fresh cilantro and dice the red onion.

On a clean, flat surface, lay out all eight sourdough slices. Spread one side of each slice evenly with the softened unsalted butter. For an extra golden and crispy crust, you can also spread a thin layer of mayonnaise on top of the butter on the buttered side.

Flip four of the buttered bread slices so the buttered side is down. Evenly layer about 1/4 cup of shredded cheese on each of these slices. Top with about 1/2 cup of the warm birria meat, then add another 1/4 cup of cheese. Place the remaining four bread slices on top, with the buttered (and optional mayo) side facing up.

Heat a large non-stick skillet or griddle over medium heat. Once hot, carefully place the assembled sandwiches in the skillet, making sure the buttered side is down. Cook for 3-5 minutes per side, or until the bread is beautifully golden brown and crispy, and the cheese is fully melted and wonderfully gooey. You might need to cook them in batches to avoid overcrowding the pan.

Carefully remove the grilled cheese sandwiches from the skillet. For that classic presentation and easier dipping, slice each sandwich diagonally in half. Serve immediately with a side of the warm birria consommé for dipping, and garnish with chopped cilantro and diced red onion, if desired. Enjoy!