12 cups (2.8 L) packed dandelion greens
2 tbsp (30 mL) butter
1 shallot, minced
1 clove garlic, minced
1/4 cup (60 mL) all-purpose flour
2 cups (500 mL) milk
1/4 tsp (1 mL) salt
1 pinch pepper
1 pinch ground nutmeg
1/2 cup (125 mL) shredded Gruyère cheese
2 tbsp (30 mL) grated Parmesan cheese
In large pot of boiling salted water, blanch dandelion greens just until tender, 2 to 5 minutes. Drain and squeeze out liquid. Coarsely chop; arrange in greased glass baking dish or shallow gratin dish.
Meanwhile, in small saucepan, heat butter over medium heat; cook shallot and garlic until softened, about 3 minutes.
Whisk in flour; cook, whisking constantly, for 1 minute. Whisk in milk, salt, pepper and nutmeg. Reduce heat and simmer, whisking occasionally, until thickened, 5 to 7 minutes.
Stir in 1/3 cup (75 mL) of the Gruyère cheese; pour over dandelion greens. Sprinkle with remaining Gruyère and Parmesan cheese.
Bake in 400°F (200°C) oven until bubbly and browned, about 25 minutes.