Heat the stock in a medium saucepan and keep it simmering over low heat.
In a medium (10 to 11-inch) pot or Dutch oven, such as Le Creuset, heat the butter and olive oil over medium heat. Add the shallots, fennel, and poblano pepper and cook for 5 minutes, stirring occasionally. Stir in the garlic, thyme, saffron, and red pepper flakes and cook for 2 minutes. Add the rice and stir to coat all the grains with butter and oil. Add the wine and cook over medium-low heat, stirring constantly, for 5 minutes, until almost all the liquid has been absorbed. Add 1/2 cup of the simmering stock to the rice and cook, stirring frequently (see Cook's Note). When the stock is almost completely absorbed, continue adding stock, 1/2 cup at a time, simmering the risotto until the stock is absorbed each time before adding more stock. Cook until the rice is al dente; it should take between 25 and 30 minutes.
When the rice is done, stir in the creme fraiche, 2 teaspoons salt, and 1 teaspoon black pepper. Fold in the crabmeat and peas and cook over low heat for 2 minutes, until the crabmeat is warmed through. Add just enough simmering stock to make the risotto moist and creamy. Serve hot in large, shallow bowls and sprinkle with chives and lemon zest.
I use either seafood stock from my fish store or canned Bar Harbor Seafood Stock.
I find that using a 1/2-cup ladle for the stock makes it easy to see how much to add.