My coworkers remembered me bringing these crostinis into the office over a year earlier, and asked me to make them again for our Christmas potluck. The flavour is outstanding, because they're topped with ingredients that were cooked veeeery slowly over low heat and are deliciously caramelized. Translation: they take time, but are soooo worth it. I made extra onions and tomatoes and used them another night to stuff chicken breasts, which I topped with Parmesan and served over cooked spinach. Don't forget, the tomatoes and onions will reduce considerably.
To make the crostinis, peel and thinly slice 6 onions. Heat 1T butter and 1T olive oil over medium-low heat in a heavy-bottomed saucepan. Add onions along with 1T sugar and 1/2 tsp salt, mix well, and cook with a lid on for the first five minutes. Then remove the lid and continue cooking for about 30-40 minutes, stirring occasionally until brown and sweet. You may need to increase heat to medium. Add 2T balsamic glaze (I use the PC brand) and cook for another 5 minutes, stirring regularly to avoid burning.
My recipe for slow-roasted candied tomatoes is here.
Slice an extra-large French baguette into crostinis about 1" thick. I used a rosemary-garlic baguette. Brush each slice with olive oil, then bake at 400 for about 5 minutes until crispy on the outside but still soft in the middle. Top each crostini with a smear of goat cheese, a small mound of caramelized onion and a candied tomato slice. Serve hot or at room temperature.