We use this Colman's packet recipe at home and it's lovely, but I'd like to recreate it myself as I'm trying to cut out gluten, plus it'll be healthier in general. It's basically just salmon fillets chucked in one of those oven roasting bags with cream, mushrooms and peas and some herbs. I've tried substituting the packet mix with just mixed herbs and it was rank. Should I try a mix of the herbs listed on the ingredients? Do I need to add something to thicken the cream? What would I use for that if I'm cutting out wheat?