In a small saucepan, bring the vegetable stock to a gentle simmer and keep warm over low heat.
In a wide heavy-bottomed pan or Dutch oven, heat the olive oil and 2 Tablespoons of the butter over medium heat. Add the shallot and cook for about 2 minutes until soft and translucent. Stir in the garlic and cook for about 30 seconds.
Add the Arborio rice and stir constantly for about 2 minutes, until the grains are well coated and the edges begin to turn slightly translucent.
Pour in the white wine and cook, stirring, until it is fully absorbed.
Add one ladle of warm stock and stir frequently until the liquid is absorbed. Continue adding stock one ladle at a time, stirring often and seasoning lightly with salt as you cook.
After about 20 minutes, begin tasting the rice. It should be tender but still slightly firm in the center.
Stir in the frozen peas and another small ladle of stock if needed. Cook for 2 to 3 minutes more until the peas are heated through and the risotto is creamy.
Remove from heat. Stir in the remaining 3 Tablespoons butter, the Parmesan cheese, mint, 1 Tablespoon of the chives, and the lemon zest. Taste and adjust seasoning with salt and pepper.
If the risotto becomes too thick, stir in a small splash of warm stock until it reaches a creamy consistency.
Spoon into bowls, garnish with the remaining chives, and serve immediately.