Heat 2 tablespoons butter in a large skillet over medium-high heat. Once foaming, add the mushrooms and cook, stirring occasionally, for 5-7 minutes until golden and their moisture has released. Season with salt and pepper, then transfer to a plate.

Reduce heat to medium. Add the remaining 1 tablespoon butter to the pan, then stir in the shallot and garlic. Cook for 1-2 minutes until fragrant, scraping up any browned bits from the bottom.

Pour in the white wine and simmer for 1 minute. Add the cream and thyme sprigs, then return the mushrooms to the pan. Simmer for 2-3 minutes until the sauce is silky and coats the back of a spoon. Taste and adjust seasoning.

While the sauce simmers, toast the bread slices until golden. Discard the thyme sprigs from the mushroom mixture, then spoon the creamy mushrooms and sauce over the toast. Serve immediately.