Finely dice bacon. Heat 1 tablespoon in a pan and fry bacon is crispy. Place on paper towels and drain.
Rinse parsnip, trim and cut into thin slices. Blanch parsnips in a pot of boiling salted water for 1 minute, drain, rinse with cold water and drain again.
Rinse corn salad and drain. Rinse tomatoes and cut into slices. Trim mushrooms and slice.
Mix vinegar in a bowl with sugar and remaining oil and season with salt and pepper. Mix prepared ingredients in a large bowl and drizzle with vinaigrette. Serve sprinkled with bacon.