peanut butter cupcakes

[new_perestroika]

It's my almost-veg coworker's last day today, and I'd like to bake her some cupcakes as a goodbye present. As we've bonded over our love of peanut butter in the past, I'm going to make the Peanut Butter Cupcakes from Vegan Cupcakes Take Over the World. Trouble is, they ask for 2 teaspoons of ground flaxseed, which I don't have, and the internet is giving me conflicting information about what to replace it with (egg replacer? oil? margarine?) I'm hoping someone here can guide me in the right direction. And if I remember, I'll update with pictures! If they look nice, anyway, which isn't generally my style.

Thanks in advance!