01 - Heat olive oil and 2 tablespoons butter in a large skillet or Dutch oven over medium heat until butter melts and foams slightly.
02 - Add sliced onions with a pinch of salt. Cook, stirring frequently, for 18-20 minutes until onions are deeply golden brown and caramelized.
03 - Stir in minced garlic and dried thyme; cook for 1 minute until fragrant, being careful not to burn the garlic.
04 - Add rice to the pan and toast for 2 minutes, stirring constantly, until grains are well coated with fat and slightly translucent at edges.
05 - Pour in vegetable broth and add bay leaf, remaining 1 tablespoon butter, salt, and pepper. Stir thoroughly to combine and bring to a rolling boil.
06 - Reduce heat to low, cover tightly, and simmer for 18 minutes until rice is tender and liquid is fully absorbed.
07 - Remove from heat, discard bay leaf, fluff rice with a fork, and let stand covered for 5 minutes to finish steaming.
08 - Fold in fresh parsley and top with grated Gruyère cheese if desired. Serve immediately while warm.