All my life, I cooked my frittatas over high heat, frantically stirring them so they'd firm up evenly before throwing them under a hellish broiler to brown and puff up. Then I read about a super low-heat baked method which is so much better for the eggs, which set at a fairly low temperature and are much more silky and tender when they've been gently cooked. So that's what this is! You can use any mix of vegetables you like, but today's version has springy broccolini, onions, and potatoes.