bring broth and 1/4 cup lemon juice to a simmer. cover and keep hot over low heat.

in medium saucepan, melt 2 tbsp butter over med heat. add shallots and saute until tender.

add rice and stir to coat with butter. add wine and remaining lemon juice, simmer until almost all evaporated.

add broth 1/2 cup at a time, stirring constantly until liquid is completely absorbed. about 20 mins.

remove from heat and stir in 1 tbsp butter, 1/2 cup parmesan, mascarpone, lemon zest, salt and pepper.

sprinkle with remaining parmesan and garnish with zest.