Place the stock, saffron and thyme in a saucepan and set it
over medium heat. Bring to a simmer, lower the heat and keep it
just below a simmer. Add the oil and butter to a risotto pan set
over medium heat. Add the shallots and cook, stirring, 2 minutes.
Add the rice and cook, stirring, until coated. Add the wine and
cook, stirring, until al the liquid has evaporated.
Add 1 cup of the heated stock to the risotto pan, and continue
stirring until all the liquid has evaporated. Repeat with 2 more
cups of stock, letting the liquid evaporate between additions.
Add a final cup of stock to the pan, scatter the shrjmp and then
the mussels over the rice, lower the heat slightly and cover the
pan. Cook until the mussels have just opened, about 4 minutes.
Using tongs, transfer the mussels to a small bowl. Remove the
pan from the heat and stir in Parmesan. (Add a bit more stock
if the risotto seems too dry.) Season with salt and pepper and
transfer to a bowl or divid among 4 dinner plates. Top with the
mussels, garnish with chopped thyme and serve.