Making brownies that calls for a 9 in sq baking pan. I have 8x8 glass pan and 9x13 glass pan. Which should I use

Always decrease the oven temp by 25 degrees when using a glass baking pan. Bake for the same amount of time but watch just in case the bake faster.

You could increase all the ingredients by about 45% - 1 1/2 times the recipe amount should be close enough.

They'll be thicker but glass will make them bake faster, so cooking time might be the same - I'd just watch them carefully.

They'll be thicker but glass will make them bake faster, so cooking time might be the same - I'd just watch them carefully.

2 options: go with the 8x8 for thicker brownies or use some heavy duty foil to create a 9x9 from the 9x13. See: http://food52.com/blog/search?query=tart+pan+hacking BUT fold one end of a large sheet over several times to make it sturdy, then line the pan with the foil so the sturdy part makes the 4th wall to prevent batter leakage.

the 8x8 should be fine. Might need a couple more minutes baking time as they'll be thicker. good luck!