I did it! With no stand mixer either. Just my little 200watt immersion blender, and when the motor gave all it could (without burning out) me with a wisk and a set of infamous dyke shoulders.
It turned out to be a heated race against time before the gelatine set and me beating enough air into the marshmallows to get them fluffy so I almost missed my melt the chocolate and add it in window. I had to hastily add partly melted chocolate, orange extract and vanilla extract and wound up with the odd chunck of chocolate in the final product.
It also meant that I was slightly late tipping the mallow out into the pan, so the whole thing stuck to the foil and was a wobbly shape because it was too stiff to smooth out. I just stuffed it into the pan to finish setting and hoped for the best (and it looks like I got it!). AFter cutting it up and coating in cocoa powder and powdered sugar, the craziness was less noticable. what was left was a nice fun orangey flavor finishing with rich chocolate and a light lingering sweetness.
success!