Pre-heat the oven to 400 degrees F and bring a large pot of salted water to a boil.
Roast The Garlic: Pre-heat the oven to 400 degrees F. Cut off the top 1/4 section of each garlic head. Place each head of garlic, cut side up, in their own piece of aluminum foil. Drizzle each head with 2 teaspoons olive oil. Wrap the aluminum foil around the garlic and crimp tightly to seal. Place the aluminum packets in the oven and roast until the garlic is soft and fragrant, approx. 45 minutes to 1 hour. Set aside to cool.
Cook the Potatoes: Bring a large pot of salted water to a boil. Peel the potatoes and dice each potato into 1" pieces. Once all the potatoes have been diced, put the diced cubes in a large colander and rinse with warm water (this helps remove excess starch). Once rinsed, add them to the pot of boiling water. Return the water to a boil and reduce the heat to medium-high. Cook until potatoes can be easily pierced with a fork (approx. 13 to 15 minutes. Transfer to the same large colander to drain. (*Note 2)
Prep the Herb Cream: Add the heavy cream, rosemary and thyme to a medium saucepan and bring to a boil over medium-high heat, approx. 5 minutes. (The mixture will bubble up vigorously, which helps reduce the liquid and concentrate the flavor.) Strain the mixture, discarding the solids, and rinse out the saucepan. Return the infused cream to the saucepan and season with salt and pepper. Cover and set aside. (You should have about 1 1/3 cups.)
Make the Garlic Potatoes: Transfer the potatoes back to the pot and add the herbed cream and butter. Squeeze the roasted garlic cloves from two garlic heads into the potato mixture and mash until creamy. Taste and season with salt and pepper. Add more roasted garlic for a stronger flavor, if desired.
Transfer mashed potatoes to a serving bowl, dot with a generous pat of butter and sprinkle with rosemary, thyme and black pepper. Top with garlic chips, and serve immediately.