Grate cheddar and parmesan. Preheat the oven to 200 degrees.
Finely chop the onion, chop the garlic.
Cut the potatoes into 0.5 cm thick slices.
Mix the cheddar with 1 teaspoon of 4 starches. Mix the Parmesan with the remaining cheese separately.
Heat oil in a frying pan. Add onion and cook until golden brown, 5-7 minutes. Add garlic and thyme, cook for another 30 seconds, pour in broth and cream.
Add potatoes, salt, and pepper. Reduce heat to medium-low, cover, and cook potatoes with cream for 10-12 minutes.
Remove from heat, add cheddar and starch and press down on potatoes so that there are no gaps.
Sprinkle the potatoes with Parmesan. Bake potatoes with cheese until golden brown, 12-14 minutes. Baked potatoes with cheese are ready.