5 medium beets, peeled, cut into 2-inch (5cm) chunks
3 medium carrots, peeled, cut into 2-inch (5cm) chunks
1 medium red onion, peeled, cut into 8 wedges
4 cloves garlic, skin on
6 sprigs fresh thyme
2 tablespoons (30ml) olive oil
½ teaspoon (3g) kosher salt, plus more
¼ teaspoon (1g) freshly ground black pepper, plus more
4 cups (960ml) chicken or vegetable broth
1 tablespoon (15ml) vodka, optional
1 tablespoon (15ml) balsamic vinegar
2 teaspoons (10g) prepared horseradish
1 teaspoon (10g) Dijon mustard
3 tablespoons (8g) chopped dill, plus more for serving
2 teaspoons (10ml) lemon juice
Sour cream, for serving
Heat oven to 400F (205C).
Toss beets, carrots, onion, garlic and thyme on a large baking sheet with olive oil, ½ teaspoon (3g) salt and ¼ teaspoon (1g) pepper. Spread into an even layer and roast for 30 minutes, stirring halfway. Once cool enough to handle, squeeze garlic from skins.
Transfer vegetables to a medium saucepan along with the broth. Bring mixture to a boil and reduce heat to maintain a simmer. Cover and cook until vegetables are very tender, about 50 to 60 minutes.
Remove thyme from saucepan then transfer mixture into a blender. Puree (in batches, if necessary) until smooth.
Return mixture to saucepan over medium-low heat. Stir in vodka (if using), vinegar, prepared horseradish, mustard, dill and lemon juice. Season with salt and pepper to taste. Cover and cook for 10 minutes.
Serve hot or cold topped with sour cream and dill.