Heat olive oil (1 Tblsp) in a large cast iron skillet over medium heat.
Once hot, add carrots, onions, and garlic.
Let cook for 8-10 minutes, until onions are clear and carrots are soft.
Add cooked lentils, thyme (1.5 tsp), rosemary (1/2 tsp), and peas (1c).
Let cook for ~5 minutes, until peas are thawed.
Smooth lentil mixture, then layer cooked mushrooms on top of lentil mixture, then add mashed potatoes on top of mushrooms.
Cook in oven at 425 degrees for 20 minutes, until edges of potatoes are light brown.*
Serve immediately with green beans, broccoli, roasted vegetables, or a salad!
Keeps in fridge for 3-4 days in a sealed container.