Cook the penne according to the instructions on the package.
Slice the chestnut mushrooms and cut the leek into rings. Rinse the leek rings in a colander. Finely chop the garlic.
In a large frying pan, sauté the mushrooms in a splash of olive oil in three batches until golden brown and cooked through.
Next, cook the leek for five minutes until softened. Remove from the pan.
Fry the plant-based bacon bits in a splash of olive oil over high heat for six minutes until crispy. Remove from the pan.
Melt the butter in the pan and add the garlic.
Stir in the flour and cook for three minutes, stirring constantly. Add a pinch of salt, then pour in the plant-based milk.
Lower the heat and let the sauce thicken while stirring.
Add the pasta, mushrooms, leek, and half of the bacon bits, then toss everything together. Divide the pasta over plates and sprinkle with the remaining bacon bits.
Season generously with freshly ground black pepper.