Preheat the oven to 350 degrees.
Cut the asparagus into 1 1/2-inch pieces, leaving the tips approximately 3 inches long.
Place the broth in a saucepan and gently warm it up. (It doesn't have to be simmering, just not cold or room temperature). Alternatively, heat it in a microwave-safe container in the microwave.
Heat 2 teaspoons olive oil and 1/2 tablespoon butter in a large oven-safe skillet or shallow Dutch oven over medium-high heat on the stovetop.
Add the asparagus and cook for 1-2 minutes or until bright green, keeping the tips separate from the rest of the stalk pieces as much as possible. Transfer to a plate to cool, keeping the tips and stems separated.
Add the remaining oil and butter to the oven-safe skillet, keeping the heat at medium-high. Add the onion, reduce heat to medium-low and cook for 4-5 minutes or until beginning to soften.
Add the garlic and cook 10-15 seconds or until fragrant.
Add the rice and coat with the fat. Cook, frequently stirring for 2-3 minutes or until most of the grains are translucent.
Add the dry white wine. Bring to a boil and cook until most of the wine has evaporated.
Add 4 cups of the warmed broth, lemon juice and zest. Bring to a boil, turn off the heat, stir, cover and place in the oven. Bake for 20 minutes. (The rice should be slightly underdone.)
Stir the risotto. It will look a little "tight," but the final addition of broth will loosen it up and make it creamy.
Return the pot to the stove on low heat. Stir in 1 cup of the remaining broth more or as needed, mascarpone cheese, 3/4 cup Parmesan cheese and half the parsley. Add the artichoke hearts, peas and asparagus stems.
Top with the asparagus tips and remaining Parmesan cheese. Serve immediately.