Place a medium sized pot over medium heat. Add the butter, shallots, garlic and jalapeño. Saute for 3-4 minutes to soften, then add the half & half and chipotle peppers.
Whisk in the cornstarch. Allow the mixture to come to a simmer, so the half & half can scald (not necessary with evaporated milk). Then lower the temperature to medium-low. Next stir in the cream cheese and mustard.
Slowly start adding the shredded cheese. Stir and add by the handful, until the sauce comes together. If you prefer your cheese sauce a little thinner, add an extra splash of half & half. Serve immediately, or keep warm in a slow cooker or fondue pot.
NOTE: If you don't like smoky flavor, use all sharp cheddar.