Shovel Knight starts the game with four orbs of health and can obtain more by acquiring Meal Tickets, giving them to the Gastronomer in the Village. There are two ways to get Meal Tickets, with one of those buying them from the Goatician just underneath the Gastronomer.
The other method to obtain Meal Tickets involves defeating the sets of The Order of No Quarter. Basically, when you defeat all of the available Knights and make the fog clear up, revealing more stages, is when you'll get a Meal Ticket. This comes from a chest at the bonfire after defeating the last Knight in the area.
Take these Meal Tickets to the Gastronomer and he'll make some food for you, similar to the food you pick up in stages to replenish your health. Only, this food will increase your health by one bubble for each Meal Ticket you give him.
