Preheat the oven to 350 degrees (180 degrees C). Butter a standard-size 6-muffin tin.

In a large mixing bowl, whisk together half and half, eggs, sugar, vanilla, and salt until well blended. Add bread cubes to liquid mixture; stir to coat all bread pieces. Divide batter evenly into the prepared muffin tin.

To prepare streusel, toss flour, brown sugar, and cinnamon together in a bowl. Cut cold butter into small pieces, then toss with flour mixture. Using a fork or pastry knife, cut the butter into the dry ingredients, until the mixture looks like a combination of coarse sand and small pebbles. Distribute streusel evenly over the 6 muffins.