In a medium skillet over medium-low heat, add 1 tablespoon olive oil and pancetta. Cook until fat is rendered, about 6 minutes. Drain pancetta on paper towels and discard all but 1 tablespoon of fat from the skillet.
Add 2 tablespoons of olive oil to the skillet and increase heat to medium-high. Return pancetta to pan and cook until crispy. Add garlic and cook until just golden, about 1 minute. Reduce heat, add thyme and stir well. Add 15 good turns of black pepper. Add vinegar, return pan to heat, and deglaze pan, scraping up all the brown bits that cling to the bottom and sides of the pan. Simmer until vinegar reduces by half. Whisk in porcini oil. Season with salt.
Put mixed greens in a salad bowl. Crumble the goat cheese over the greens. Quickly toss mixture with pancetta dressing so greens barely wilt. Drain cherries. Add cherries, toss again. Immediately transfer to plates and serve.