Run the chicken leg fillets through a mincer twice so they are finely ground.
On a cutting board, with a sharp knife, dice the Florina pepper and finely chop the onion and garlic.
Heat a large deep non-stick pan over high heat, add the olive oil, and sauté the onion, garlic and pepper for 2–3 minutes, stirring so they soften without browning.
Add the chicken mince; sauté, breaking it up well, and season with salt and freshly ground pepper.
Deglaze with the white wine. Stir in the tomato paste, diced tomato and chicken stock.
When the mixture comes to a boil, lower the heat and simmer until the mince is cooked and the sauce has thickened.
While the mince is cooking, melt the butter in a saucepan over medium heat. Stir in the flour; when combined, add the milk, whisking constantly until the cream thickens.
Remove the pan from the heat and beat in the yolks, nutmeg, grated graviera, salt and freshly ground pepper and stir well.
Spread a thin layer of béchamel in a small Pyrex dish and sprinkle with a little graviera cheese.
Fill the cannelloni with the chicken mince and arrange them side by side in the dish.
Cover with the remaining béchamel and sprinkle with the remaining graviera.
Bake in a pre-heated oven at 180 °C for 25–30 minutes.
Remove from the oven and let the cannelloni stand a few minutes before cutting and serving.
