Heat a wide pan over medium heat and add the olive oil. Once shimmering, toss in the sliced mushrooms and cook until they release their earthy aroma and turn golden brown, about 8 minutes. Remove and set aside.
Add butter to the same pan, letting it melt gently. Stir in the finely chopped onion and cook until translucent and sweet-smelling, around 3-4 minutes.
Mix in the minced garlic and cook for just 30 seconds until fragrant, filling the kitchen with a savory aroma.
Add the Arborio rice to the pan, stirring constantly. Toast the grains for about 2 minutes until they look translucent at the edges and smell nutty.
Pour in ½ cup of warm vegetable broth and stir until mostly absorbed, then continue adding broth in ½ cup increments, stirring gently each time. Keep the heat low to medium, maintaining a gentle simmer, and stir continuously.
After about 20 minutes, the rice should be tender yet slightly firm (al dente), and the mixture will be creamy and glossy. If it gets too thick, add a splash more warm broth and stir to loosen.
Stir in the sautéed mushrooms, grated Parmesan, and the chopped herbs. Mix well until everything is combined and heated through.
Taste and adjust seasoning with salt and pepper if needed. Let the risotto rest off the heat for 2 minutes to settle and deepen in flavor.
Scoop the risotto into warm bowls, garnish with extra herbs if desired, and serve immediately to enjoy its creamy, earthy goodness with a fragrant aroma filling the room.