Heat the oil in a pan and cook the shallot and chorizo for 5 mins until the shallot is softened. Stir in the chicken and tomatoes. Remove from the heat.
Put half the tortillas onto baking sheets. Spread a little chicken mixture on each one. Scatter over the cheese and coriander. Sandwich with the remaining tortillas. You can make up to this point 2 hrs ahead.
Heat oven to 180C/fan 160C/gas 4. Cook the tortillas for 3 mins. Using a fish slice, turn each one over. Cook for 3 mins more until both sides are golden. Put on a board, slice into wedges and serve.