Melt the butter in a large skillet, or Dutch oven, set over medium/high heat. Add the onions, garlic, and sugar. Stir everything together to evenly combine.
3 large yellow onions, 6 tbsp butter, 4 cloves garlic, 1 tsp brown sugar
Cook, stirring often, for 10 minutes on high heat, then reduce the heat. Reduce the heat to medium and continue cooking, stirring often, for 15 more minutes- until the onions are a deep golden brown color. Stir constantly so they don't crisp or burn.
Add the broth, seasonings, and bay leaf to the pot. Stir everything together to evenly combine then bring the mixture to a simmer. Stir in the tortellini & heavy cream, then cook for 3-5 minutes, just until the tortellini's done, stirring often.
1 cup beef broth, 1/2 tsp dried sage, 1/2 tsp dried thyme, 1/8 tsp crushed red pepper flakes, salt & pepper, 1 bay leaf, 1 19 oz pkg refrigerated cheese tortellini, 1 cup heavy cream
Remove the pot from heat, and remove the bay leaf and discard.
Add 1 1/2 cups of cheese to the pasta and stir until fully incorporated and the sauce is smooth, thick, and creamy.
2 cups shredded gruyere cheese
Spread the pasta out in the pot in an even layer, then sprinkle the remaining cheese evenly out overtop. Cover and let rest for 2-3 minutes for the cheese to melt.
Serve warm and enjoy!