Preheat oven to 375 degrees F. Lightly spray a baking sheet with oil or line it with parchment paper, and set aside.
Heat a large skillet over medium-high heat. Add the chopped bacon pieces to the hot skillet and cook until the bacon begins to get crispy. Remove the cooked bacon to a plate lined with a paper towel. Leave 2 tablespoons of bacon drippings in the skillet and discard any extra that remains.
Add the sliced onions to the skillet and sauté over medium-high heat for 10-12 minutes, until the onions caramelize. Add the cooked bacon back in and stir in the balsamic vinegar, brown sugar, and 1 tablespoon of the thyme leaves. Reduce heat to low and cover with a lid. Simmer for 10 minutes. Remove from heat and cool slightly.
While the jam is cooling, toast the baguette slices. Place the baguette slices onto the prepared baking sheet. Using a pastry brush, brush the olive oil over each slice. Place the baking sheet in the preheated oven and bake for 10 minutes, until lightly toasted.
To a mixing bowl, add the goat cheese, grated garlic, and the remaining thyme. Using an electric mixer, mix on medium speed for 2-3 minutes, until it transforms into a smooth consistency.
Spread a dollop of the whipped goat cheese onto each toasted crostini. Top with a spoonful of the bacon onion jam, and garnish with fresh thyme leaves.