Bring a large pot of water to a boil. Add perogies and cook stirring occasionally for 6 mins. Drain and set aside.
In a large skillet over medium heat, melt butter with oil. Add garlic, leeks, thyme and season with salt and pepper, sauté for 3-4 mins until garlic is translucent and leeks have softened.
Add perogies to the skillet and sauté for another 1-2 mins stirring to mix well.
Place on platter and serve warm.