In a small bowl, whisk together the lemon juice, olive oil, Dijon mustard, minced garlic, salt, and black pepper until emulsified. This creates a balanced vinaigrette where the mustard acts as an emulsifier to help the oil and lemon juice stay combined. Set aside while you prepare the peas.

Bring a pot of salted water to a boil and add the peas, cooking for exactly 3 minutes—this brief cooking time keeps them bright green and slightly tender without becoming mushy. Immediately drain and plunge them into a bowl of ice water to stop the cooking process and set their color. Once cooled, drain thoroughly and pat dry with a paper towel; I find that excess moisture on the peas can dilute the dressing, so this step is important for the final texture.

In a large bowl, combine the cooled peas from Step 2 with the dressing from Step 1, tossing gently to coat evenly. Add the fresh mint and crumbled feta cheese, folding everything together carefully to avoid breaking up the feta too much—those 1/2-inch chunks add nice pockets of creamy, salty flavor. Top with sunflower seeds just before serving for a pleasant crunch that won't get soggy.