Directions

1. Heat a large heavy saucepan over medium-high heat. Add the bacon and cook, stirring often, for about 5 minutes, or until golden brown. Using a slotted spoon, transfer the bacon to paper towels to drain, leaving the drippings in the saucepan. Add the shallots to the saucepan and cook, stirring often, for about 2 minutes, or until translucent. Add the garlic and saute for about 1 minute, or until fragrant.
2. Reduce the heat to medium-low, whisk in the flour, and cook, whisking, for about 1 minute. Gradually whisk in the milk and cream, then bring the sauce to a gentle simmer over medium heat and simmer, whisking often, for about 10 minutes (do no allow the sauce to boil). Reduce the heat to medium-low and gradually whisk in the Gruyere and Cheddar cheese. Remove the pan from the heat and season the sauce to taste with salt and pepper; it will seem thin at this point.
3. Meanwhile, bring a large pot of salted water to a boil over high heat. Stir in the penne and cook, stirring often to prevent it from sticking together, for about 8 minutes, or until tender but still firm to the bite. Drain well.