Boil potatoes in enough water to cover them with 1/2 teaspoon of salt for 10-12 minutes or until tender enough to easily pierce with a skewer or small knife.
Add 1 tablespoon bacon fat and mustard to the pot and stir around until the fat is melted and the potatoes are coated.
Dump onto a cast iron skillet or baking sheet and mash each potato with the bottom of a glass.
Spoon whatever mustard is left in the pot over the potatoes.
Sprinkle tops with bacon bits, thyme, remaining salt and pepper.
Bake 15-20 minutes until brown and toasty.
Also try this with:
Several whole garlic cloves added to the pan
Sesame seeds instead of thyme
Rosemary or oregano instead of thyme
Paprika or cayenne pepper instead of black pepper
Duck fat, butter, or olive oil instead of bacon fat