Lobster Risotto - 2 1/2 lbs

Ingredients

 

4 cups chicken stock, 2 cups lobster stock, 3 tbsp. olive oil, 3 medium shallots, minced, 2 cloves garlic, minced, 2 cups arborio rice, 1/3 cup dry white wine, 1/2 cup mascarpone, 1 lb. Maine lobster meat, cut into 1" pieces, 1/2 cup frozen peas, 3 Tbsp. unsalted butter, 1 Tbsp. fresh lemon juice, plus 1 tsp. lemon zest, 2 Tbsp.chopped tarragon, plus more for garnish