Heat the oil in a large, deep sauté pan
or saucepan. Tip in the onion and thyme
sprigs and fry for 2-3 mins. Then add the
carrots and fry together for 5-8 mins,
stirring occasionally until the vegetables
start to brown. Stir in the mince to break
it down. Fry for 1-2 mins until no longer
pink. Stir in the flour, scraping the bottom
of the pan in case the meat sticks, then
cook for another 1-2 mins. Pour in the
stock and stir until thickened. Stir in
the tomatoes, tomato purée, lentils and
Worcestershire sauce and season with
pepper. Reduce the heat and simmer,
covered, for 45 mins, stirring occasionally.
Meanwhile, prepare the topping. Drop
all the potatoes into a large pan of boiling
water. Bring back to the boil, then
simmer for 12-15 mins or until the
potatoes are tender. Drain well in a
colander then tip back into the pan. Mash
with a masher or, briefly, with an electric
hand mixer until smooth. Beat in the
crème fraîche and milk with a wooden
spoon until light and fluffy. Heat oven to
200C/180C fan/gas 6.
Spoon the meat into a 1.5 litre pie dish
and remove the thyme sprigs. Top with
the mash and smooth over with a knife.
Use a fork to create a ridged pattern on
top. Place the dish on a baking sheet
and bake for about 20-25 mins until
piping hot and the filling starts to bubble
around the edges. If the top is not brown
enough, pop it under the grill for 5 mins
or so until the mash is crisp and golden.
Let it sit for 5 mins then serve.