- In a small bowl, dissolve the cornstarch in the water. Set aside.
- In a saucepan, melt the butter. Add the flour and continue cooking for about 5 minutes, stirring constantly, until the mixture (the roux) turns golden brown. Stir in the garlic and continue cooking for 30 seconds.
- Add the beef and chicken broths and bring to a boil while stirring with a whisk. Stir in the dissolved cornstarch mixture and simmer for 3 to 5 minutes or until the gravy thickens. Season with the cayenne pepper.
- With two racks in the middle positions, preheat the oven to 450°F (230°C). Line two baking sheets with silicone mats or parchment paper.
- On a work surface, cut all of the vegetables, except the beans, into 1/2-inch (1 cm) thick sticks. Spread the russet or Yukon Gold potatoes, carrots and parsnips on a baking sheet. Toss to coat with 2 tbsp (30 ml) of the olive oil and season with salt and pepper. Bake for 15 minutes. Remove from the oven and turn the vegetables.
- Meanwhile, on the second baking sheet, spread the sweet potatoes and green beans. Drizzle with the remaining oil (1 tbsp/15 ml) and season with salt and pepper. Bake both sheets of vegetables for 15 minutes or until the vegetables are tender and lightly browned.
- Transfer the vegetables to shallow serving plates. Sprinkle the cheeses over the vegetables. Drizzle with the warm gravy. If needed, return to the oven for about 3 minutes to melt the cheeses.
This recipe contains 12 servings of vegetables (not counting the potatoes!).