Bring a large pot of salted water to a boil. Add farfalle and cook until tender with a bite, about 11 minutes, stirring occasionally. Drain pasta, reserving 1/2 cup of pasta water to thin the sauce later if needed.

Meanwhile, heat a large skillet over medium heat. Add bacon; cook, turning occasionally, until crisp, 3 to 5 minutes. Transfer bacon to a paper towel to drain. When cool enough to handle, crumble and set aside. Remove bacon grease from skillet.

Heat oil and butter in the skillet over medium heat; add mushrooms and onions. Cook until onions are translucent and the moisture in mushrooms is starting to evaporate, 3 to 5 minutes, stirring occasionally.

Stir in garlic, and cook until fragrant, about 30 seconds.

Reduce heat to low, stir in half-and-half, peas, and thyme. Bring to a gentle simmer, and cook until peas are heated through and sauce has started to thicken, 3 to 4 minutes. If sauce is too thick, add a little reserved pasta water to thin.