01 - Combine olive oil and 2 tablespoons butter in a large skillet or Dutch oven over medium heat until melted and shimmering.
02 - Add sliced onions with a pinch of salt. Cook stirring frequently for 18-20 minutes until 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 and slightly translucent at edges.
05 - Pour in vegetable broth. Add bay leaf, remaining 1 tablespoon butter, salt, and pepper. Stir thoroughly and bring to a 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 before serving.
08 - Fold in fresh parsley. Top with grated Gruyère cheese if desired. Serve warm as a side dish or vegetarian main.