• Heat oven to 350°F.

Cook the potatoes

• Put the peeled and quartered potatoes in a pot and cover with cold water. Place pot on a stove burner, turn to high heat, and bring to a simmer (this takes 5-6 minutes).
• Reduce heat to medium-high and simmer until potatoes are just fork tender (10-15 minutes). During this time, adjust heat as needed to keep at a simmer and not a violent rolling boil.
• While potatoes are cooking: in a small saucepan, melt the butter. Add the garlic and cook gently for 1 minute to infuse the butter and lightly cook the garlic. Remove from the heat and set aside.

Assemble the mashed potatoes

• Drain potatoes well. If using a potato ricer, pass the potatoes through the ricer back into the empty pot. If not using a ricer, put drained potatoes back in the pot and mash.
• Add the butter-garlic mixture, cream, milk, 3/4s each of the Gruyere and Gouda cheeses, salt, pepper, 1 Tablespoon each parsley and chives, and 1/2 Tablespoon tarragon. Stir together.
• Add a splash or two more milk if necessary to the desired consistency of creamy mashed potatoes.

Bake and serve

• Transfer mashed potatoes to a 2-qt casserole or bake dish. Top with the remaining Gruyere and Gouda.
• Bake, uncovered at 350°F for 20 minutes until heated through with an audible little sizzle. Top with remaining herbs and serve.