Heat oven to 375 degrees and position rack in lower third. Butter a one-quart casserole dish and dust with flour, shaking out excess. In a bowl, whisk ricotta, egg yolks, salt, and herbs. Season with pepper. In a separate bowl, whisk whites until stiff peaks form. Working in two batches, gently fold whites with a large rubber spatula into ricotta mixture until just combined.
Pour mixture into prepared dish and bake until puffed, golden brown, and firm to the touch, 30 to 32 minutes.
Beat whites with a balloon whisk (for more air per stroke) or a mixer with a whisk attachment.