Start by preparing the garnish; whisk together the garlic, mayonnaise, soured cream and paprika in a small mixing bowl until smooth. Season to taste, then cover and chill until needed. Prepare the fajita filling by heating the olive oil in a large frying pan set over a moderate heat. Saute the pork for 6-8 minutes, stirring occasionally, until golden brown in colour all over. Add the onion and peppers and stir well. Reduce the heat a little and cover the pan for 2-3 minutes to allow the steam to soften the vegetables and the pork to cook through. Remove the lid and add the cumin, paprika and some seasoning and continue to cook for 2-3 minutes before removing from the heat. Heat another frying pan over a medium heat for 1 minute, then warm the flour tortillas in it for 10-15 seconds on both sides until warmed. Lay on a flat surface and spoon the filling into the centre of them. Top with a little of the prepared soured cream sauce, then roll up and arrange on plates with the seam underneath to hold them in place. Serve immediately with a sprig of coriander as a garnish.