Sugar Won't Dissolve!

[doodle]

I've made butter tarts for 40 years.

basic ingredients-- brown sugar, butter, vinegar, vanilla, cream & egg

now that I am putting my filling into my gluten-free tart shells the brown sugar does not want to "dissolve" and it also creates a thin sugar coating over the pastry instead of blending with the other ingredients to cook properly

FYI- I am using a commercial convection oven but at a lower temp than an electric one - ie. 325 on the convection dial so as not to burn or dry out the pastry = btween 360 to 375 F in an electric

does anyone have any thoughts as to why this is happening?

doodle

[ang1e0251]

Do you cream the butter and sugar very well before baking? Have you ever used the gluten-free shells with your conventional oven instead of convection?

[lpellegr]

If the sugar gets mixed in with the other ingredients before you put it into the tart shell, I'd say you need to compensate by mixing it more. Rebecca Reilly's gluten-free baking book stresses how you need to cream the butter and sugar for a long time to make sure the sugar is dissolved. If you are doing everything else the same as when you used to use regular tart shells, but the lower temperature is the only difference, I'd say either try raising the temperature back up (maybe cover the edges of the tart shells with foil so they brown less) or try mixing like crazy to get the sugar better incorporated in a way that the heat used to take care of.