Pre-making pastilla filling I should start by stating my actual problem: this coming Rosh HaShannah, the latest I can buy fresh meat is on Thursday, but I need to serve it the following Monday. (Jewish holiday. I live in Israel, shops are going to be closed.)

I thought to circumvent having to either freeze the meat, or reheat a prepared dish, by way of pre-making pastilla filling on Friday or Saturday, keeping it in the fridge, and only baking the actual pastilla on Monday, before serving.

Would such a solution be safe to eat? Would the filling keep its taste, being refrigerated for several days?
I'm in the US and when we buy fresh chicken at the market it has a 'sell by' date. It's safe to assume that it will be good for one to two days after that date, as long as the chicken is stored properly. If this is the case for you, try and get your chicken with a sell by date of at least Saturday. Then you can be assured it will be okay on Sunday or Monday when you make your filling. Just be sure to get it home and in the refrigerator right away.

If this is not an option for you, there are a couple of things you can do: 


Assuming you buy your chicken on Thursday, take it home and put it in the freezer right away. On the day before you wish to make your filling, place it in the refrigerator to thaw overnight. Then proceed as usual. A very short time frozen should not affect the quality or taste of your meat.
You can make your filling in advance and refrigerate it. After cooking, chicken should be okay in the refrigerator for three to four days. So, you can make your filling on Friday or Saturday and refrigerate it until you bake your pastilla on Monday. I wouldn't think this would hurt the flavor in any way. Many times the overall flavor can actually improve as the flavors have time to meld together.