Bring a large pot of water to a boil.
In a large skillet, heat the EVOO, two turns of the pan, over medium- high. Add the chicken and season with salt and pepper. Cook until lightly browned, stirring often, about 4 minutes. Add the onion, carrot, celery, garlic and bay leaf; season. Cook, partially covered and stirring occasionally, until the vegetables soften, 7 to 8 minutes. Add the paprika and cayenne and stir to toast the spices, about 1 minute. Add the stock and tomatoes; reduce the heat and let the goulash simmer while the pasta cooks.
Salt the water and cook the pasta until al dente. Drain, reserving 1/2 cup of the pasta cooking water. Add the pasta and the cooking water back to the hot pot. Add the butter and herbs; toss to coat. Add the lemon juice and season with salt.
Off heat, stir the creme fraiche into the goulash. Toss the goulash with the pasta and divide among shallow bowls.