In a large pot, add butter, olive oil, and sliced onions. Cook on high for 5-10 minutes until the onions start to sweat and become translucent. Reduce heat to low, cover and simmer for about 40 minutes until the onions brown and caramelize, stirring every 10 minutes or so to avoid burning. Onions will reduce significantly.

Once they are brown and jammy, bring heat up to medium high, add garlic, salt, and 1 whole bunch of thyme. Sauté until fragrant, then deglaze pan with red wine, scraping any browned bits in the bottom. Add beef broth, bay leaf, and pasta, bring to a simmer and cook for 10 minutes until the pasta is al dente. Continue stirring every so often to avoid sticking. Once the pasta is cooked and most of the broth absorbed, remove from heat and stir in the cheese.

Meanwhile, melt 1/2 cup butter with 1 tbsp of thyme leaves, mix in panko and season with salt and pepper. Transfer pasta into a casserole dish and generously top with breadcrumbs. Bake 15 minutes at 400F/205C until panko has browned.