Preheat oven to 300°F.
Line an 9-inch springform pan with parchment paper. Spray the parchment paper with baking spray.
Toast the almonds and hazelnuts under the broiler until lightly brown. Set aside to cool.
In a large mixing bowl, toss together nuts, candied fruit peel, spices, salt, and flour.
Combine the sugar, honey, and butter in a saucepan. Cook until mixture reaches the softball stage on a candy thermometer (25o°F) or when the hot mixture forms a soft ball when dropped in a small glass of cold water.
Pour the hot syrup over the dry ingredients and mix quickly before it sets. Pour into pan and smooth the top with the back of a large spoon until even.
Bake 30-35 minutes. Remove from oven and let sit until it firms up enough to remove from pan. Remove parchment paper. Heavily dust the top and bottom of panforte with confectioner’s sugar.
Store in a tightly sealed tin at room temperature up to two months.