Preheat the oven to 425 degrees F. Arrange the top rack in the oven 4-6 inches from the broiler and another rack in the middle.
In a square, round or oval baking dish, combine the grapes, garlic, shallots, salt, pepper, olive oil and balsamic vinegar.
Break the block of feta into 1-inch to 1-1/2-inch pieces. Stir the cheese with the grapes. Then arrange the feta and grapes, so they are mostly in a single layer packed tightly against each other. Put the thyme sprigs on top.
Bake the feta for 18-20 minutes, until it starts browning at the edges and the grape skins starts to wrinkle.
Turn the broiler on high. Drizzle the honey over the feta. Then broil the cheese until it’s nicely browned, about 2-3 minutes. Rotate the baking dish as needed.
Sprinkle the feta and grapes with walnuts before serving with toasted baguette slices, crackers or pita chips.