In a medium saucepan, warm the broth and keep it at a low simmer.
In a separate large pan, heat olive oil and 1 tbsp butter over medium heat. Add the diced onion and cook until soft and translucent, about 5 minutes.
Add the garlic and cook for another minute until fragrant.
Stir in the arborio rice and cook for 2-3 minutes to toast slightly.
Add 1 ladle of warm broth to the rice and stir gently until absorbed. Continue adding broth one ladle at a time, stirring often and allowing each addition to absorb before adding the next.
After about 15 minutes, stir in the asparagus and peas. Continue cooking for another 5–7 minutes until the vegetables are tender and the rice is creamy but still al dente.
Remove from heat and stir in the remaining butter, parmesan cheese, and lemon juice. Season with salt and pepper to taste.
Garnish with fresh herbs if desired and serve immediately.