Place the saffron and boiling water in a cup and allow to steep for 5 minutes. Heat a saucepan with butter over medium heat. Melt the butter and add the onions and cook until translucent.

Add the rice and cook until slightly toasted, about 3 minutes. Add the saffron water, salt, and vegetable broth. Bring to a boil and then reduce the heat to low. Cover and cook until the rice has cooked, about 20 minutes.

Preheat your oven to 425°Bring a pot of water to a boil and add the potatoes and carrots. Cook for 8 minutes. Transfer the potatoes and carrots to a bowl with mushrooms and olive oil.

Place the oiled vegetables on a baking sheet and sprinkle with salt and pepper. Bake for 20 minutes, toss, and bake for another 15 minutes.

While the vegetables are roasting, combine the garam masala, cardamom, turmeric, paprika, coriander, cumin, chili powder, and cinnamon in a small bowl. Heat a large pan with butter over medium-high heat. Add the red onion and cook until translucent, about 5 minutes. Add the garlic and ginger paste and cook until fragrant, about 2 minutes. Add the spice mixture and mix until well combined.

Add the crushed tomatoes and vegetable broth. Mix well, making sure there are no clumps of spices left. Simmer for 5 minutes.

Add the yogurt and honey. Taste and season with salt and pepper if needed. Add the roasted vegetables. Serve with saffron rice.