It could be the soft lighting and rich hues of creamy taupe, burgundy, and deep orange in the dining room. Maybe it's the Francophile's dream of a wine list. It might even be the comfortable and confident service. But ultimately we think it's chef Mark Allen's food that pushes the romance quotient at his Newton restaurant Le Soir to hot and steamy. The heady aromas of chanterelle mushrooms, truffle oil, and even slowly cooked rabbit potpie fill the air while the sensuous textures of crispy-skinned roast duck fill your mouth. A meal here with anyone is special, but with your significant other, it's a night to remember.